The monohydrates of the four polar dipeptides L-seryl-L-asparagine, L-seryl-L-tyrosine, L-tryptophanyl-L-serine and L-tyrosyl-L-tryptophan

The crystal structures of the four dipeptides L-seryl-L-aspara­gine monohydrate, C₇H₁₃N₃O₅·H₂O, L-seryl-L-tyrosine monohydrate, C₁₂H₁₆N₂O₅·H₂O, L-tryptophanyl-L-serine monohydrate, C₁₄H₁₇N₃O₄·H₂O, and L-tyrosyl-L-tryptophan mono­hydrate, C₂₀H₂₁N₃O₄·H₂O, are dominated by extensive hy­drogen-bonding networks that include cocrystallized solvent water mol­ecules. Side-chain conformations are discussed on the basis of previous observations in dipeptides. These four dipeptide structures greatly expand our knowledge on dipeptides incorporating polar residues such as serine, asparagine, threonine, tyrosine and tryptophan.

S1. Comment

A total of 36 dipeptides can be constructed from the six polar residues Asn, Gln, Ser, Thr, Tyr and Trp, but the structure of only one, Tyr–Tyr hydrate (Cotrait et al., 1984), has been investigated previously by single-crystal X-ray diffraction. The title molecules, Ser–Asn hydrate (SN), Ser–Tyr hydrate (SY), Trp–Ser hydrate (WS) and Tyr–Trp hydrate (YW), were studied as part of an effort to increase our knowledge of such dipeptides. The asymmetric units of the four dipeptides are shown in Fig. 1, while essential torsion angles are listed in Tables 1, 3, 5 and 7. The molecules occur in unconstrained, extended conformations with close to planar peptide bonds and deviations from a perfectly staggered orientation of the amine group reaching a maximum value of 25° for YW.

The side-chain conformations for the title compounds were compared with those of related dipeptides in the Cambridge Structural Database (CSD; Version 5.29 of November 2007; Allen 2002). It is noted that the side chains of N-terminal Ser residues in the CSD are always in a gauche- orientation (the gauche+/trans/gauche- distribution is 0:0:5), while C-terminal Ser on the other hand displays a 7:5:1 distribution. An opposite trend is found for Trp, with distributions of 3:0:0 and 1:0:5 for N-terminal and C-terminal residues, respectively. Tyr has the same preference as Trp for gauche+ at the N-terminus (5:2:1), but uniquely has trans as the most favoured C-terminal orientation (1:3:1). There are only two other dipeptides with a C-terminal Asn residue in the CSD, one each in a gauche+ and gauche- orientation. The side-chain conformations found for the four title dipeptides (Tables 1, 3, 5 and 7) agree with the CSD statistics; only for the Tyr residue of SY do we find a conformation (gauche+) that is not also the most frequently observed among dipeptides in the CSD (trans).

It is noteworthy that all four polar dipeptides have been obtained as hydrates. This observation is of particular interest for WS and YW, as all seven dipeptides with a Trp residue in the CSD are also hydrates, indicating a very high propensity for cocrystallization with water molecules for this particular residue. In contrast, SN is the first Ser–Xaa (Xaa = any amino acid) dipeptide to crystallize as a hydrate.

Among the four dipeptides studied, SN has the smallest hydrophobic units in the side chains, which generate inconspicuous hydrophobic columns along the short (4.75 Å) a axis (Fig. 2). Accordingly, the hydrogen-bonding network is three-dimensional, and as in all N-terminal Ser-residue dipeptide crystal structures, the hydroxy H atom hydrogen bonds to a carboxylate acceptor (Table 2). This group also accepts two of the amino H atoms, but the third amino H atom, which is usually donated to the Ser hydroxy group, is instead accepted by the cocrystallized water molecule that acts as a bridge between the two groups.

Unlike SN, the crystal packing of SY (Fig. 3) is clearly divided into layers. There is, however, only one head-to-tail chain involving the charged N– and C-terminal groups (Table 4). The remaining two amine H atoms are accepted by the hydroxy groups of the Ser and Tyr side chains. Adding to the three-dimensional hydrogen-bonding pattern, the hydroxy groups also act as donors and span the main chain layers by interacting with the carboxylate groups in a direct fashion for the Tyr OH group and in an indirect fashion, using the cocrystallized water as a bridging molecule, for the Ser OH group sitting on a shorter side chain. The extra OH group of Tyr compared with Phe means that SY has a completely different structure from Ser–Phe (Helle et al., 2004). Glu–Glu (Eggleston & Hodgson, 1982), on the other hand, shows some of the same traits, with the N-terminal Glu replacing the Ser residue as well as the cocrystallized water molecule in SY.

The structure of WS adds to a series of structures of dipeptides with a C-terminal Ser residue studied previously, including Gly–Ser (Görbitz, 1999), Leu–Ser (Görbitz et al., 2005), Val–Ser trihydrate (Johansen et al., 2005), Val–Ser trifluoroethanol solvate (Görbitz, 2005), Ile–Ser hydrate, Met–Ser hydrate and Phe–Ser (Görbitz et al., 2006), Ala–Ser hydrate (Jones et al., 1978), Arg–Ser acetate hydrate (Verdaguer et al., 1991), and His–Ser in complex with Gly–Glu (Suresh & Vijayan, 1985). In this group, Ile–Ser and Met–Ser have rather similar structures, while all other compounds have individually unique crystal packing arrangements. This is also true for WS, shown in Fig. 4, which, as expected from a dipeptide with large hydrophobic entities, is clearly divided into layers. The hydrogen-bonding pattern (Table 6) is nevertheless completely different even from that of its presumably closest relative Phe–Ser (Görbitz et al., 2006). The most unusual feature is the amine H atom that is not involved in a strong hydrogen bond to an O-atom acceptor, but instead is squeezed in between two Trp side chains where it acts as a donor in weak inter- and intramolecular interactions with C-atom acceptors (Desiraju & Steiner, 1999; Fig. 5).

The structure of YW (Fig. 6) has a `Big Mac' construction, with two different types of hydrophobic layers, one generated from Tyr side chains and one from Trp side chains, separated by the same type of hydrophilic layers constituted by the peptide main chains. The same pattern was found for the related compounds Tyr–Val (Ramakrishnan et al., 1984), Tyr–Leu (Ramakrishnan & Viswamitra, 1988) and Tyr–Phe (Murali & Subramanian, 1987). It follows that the N^εH donor of the Trp side chain is involved only in a comparatively weak interaction, with the C atom (C14) of a neighbouring Trp side chain as the acceptor (Table 8). The hydrogen-bonding pattern of this group of dipeptides is furthermore interesting in that, as for WS, one of the amine H atoms does not participate in a strong N—H···O interaction. Instead it is sandwiched between two aromatic rings, where it is involved in weaker intermolecular and intramolecular N—H···C contacts (Fig. 7). The complete absence of direct head-to-tail interactions between the charged N-terminal and C-terminal groups in YW is a very rare phenomenon for dipeptide structures.

In summary, all four dipeptides display extensive hydrogen-bonding networks, but the gradual increase in the size of hydrophobic units in the side chains from SN through SY and WS to YW shifts the hydrophobic aggregation pattern from columns to layers and the dimensionality of the hydrogen-bonding pattern from three- to two-dimensional when only strong N—H···O and O—H···O interactions are considered. The presence of a large number of hydrogen-bonding donors and acceptors, including those present in cocrystallized water molecules, makes it possible for polar dipeptides to fulfil their hydrogen-bonding requirements while retaining peptide main chains and side chains in unconstrained conformations, but in both dipeptides with a Trp residue, WS and YW, unusual (amine)N—H···C(π) interactions are observed.

Related literature

For related literature, see: Allen (2002); Cotrait et al. (1984); Desiraju & Steiner (1999); Eggleston & Hodgson (1982); Görbitz (1999, 2005); Görbitz et al. (2006); Görbitz, Nilsen, Szeto & Tangen (2005); Helle et al. (2004); Johansen et al. (2005); Jones et al. (1978); Murali & Subramanian (1987); Ramakrishnan & Viswamitra (1988); Ramakrishnan et al. (1984); Suresh & Vijayan (1985); Verdaguer et al. (1991).

S2. Experimental

The title compounds were obtained from Bachem. Crystals were obtained by slow diffusion of acetonitrile into 30 µl of an aqueous solution containing about 0.2–2.0 mg of the peptide depending on the solubility.

S3. Refinement

Positional parameters were refined for all H atoms of SN. For the three other structures, positional parameters were refined only for H atoms involved in short hydrogen bonds. Other H atoms were positioned with idealized geometry and fixed C—H distances in the range 0.95–1.00 Å. U_iso values were set at 1.2U_eq of the carrier atom, or 1.5U_eq for the amine and hydroxy groups as well as for cocrystallized water molecules. In the absence of significant anomalous scattering effects, Friedel pairs were merged.

Computing details

For all compounds, data collection: SMART (Bruker, 1998); cell refinement: SAINT (Bruker, 2001); data reduction: SAINT (Bruker, 2001); program(s) used to solve structure: SHELXTL (Version 6.10; Sheldrick, 2008); program(s) used to refine structure: SHELXTL (Version 6.10; Sheldrick, 2008); molecular graphics: SHELXTL (Version 6.10; Sheldrick, 2008); software used to prepare material for publication: SHELXTL (Version 6.10; Sheldrick, 2008).

Figures

	Fig. 1. : The molecular structure of SN (top, left), SY (top, right), WS (bottom, left) and YW (bottom, right). Displacement ellipsoids are shown at the 50% probability level and H atoms are shown as spheres of arbitrary size.
	Fig. 2. : The crystal packing arrangement of SN viewed approximately along the a axis, with hydrophobic parts of the Ser and Asn side chains (in yellow in the online version of the journal). In Figs. 2, 3, 4 and 6, non-essential H atoms have been omitted for clarity, while short hydrogen bonds are indicated by dashed lines.
	Fig. 3. : The crystal packing arrangement of SY viewed approximately along the c axis, with hydrophobic parts of the Ser and Tyr side chains (in yellow online).
	Fig. 4. : The crystal packing arrangement WS viewed along the a axis.
	Fig. 5. : A structural detail showing amineN—H···C interactions in WS, with H···C distances in Å.
	Fig. 6. : The crystal packing arrangement viewed along the a axis for YW (top) and for Tyr–Leu (Ramakrishnan & Viswamitra, 1988) (bottom).
	Fig. 7. : A structural detail showing amineN—H···C interactions in YW, with H···C distances in Å.

(SN) L-Seryl-L-asparagine monohydrate

Crystal data

C7H13N3O5·H2O	Z = 1
Mr = 237.22	F(000) = 126
Triclinic, P1	Dx = 1.493 Mg m^−3
a = 4.7547 (1) Å	Mo Kα radiation, λ = 0.71073 Å
b = 7.5121 (2) Å	Cell parameters from 2419 reflections
c = 8.5626 (2) Å	θ = 2.7–28.3°
α = 115.691 (1)°	µ = 0.13 mm^−1
β = 90.266 (1)°	T = 105 K
γ = 104.957 (1)°	Block, colourless
V = 263.87 (1) Å^3	0.30 × 0.25 × 0.20 mm

Data collection

Siemens SMART CCD diffractometer	1289 independent reflections
Radiation source: fine-focus sealed tube	1281 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.017
Detector resolution: 8.3 pixels mm^-1	θmax = 28.3°, θmin = 2.7°
Sets of exposures each taken over 0.3° ω rotation scans	h = −6→6
Absorption correction: multi-scan (SADABS; Sheldrick, 1996)	k = −9→10
Tmin = 0.838, Tmax = 0.974	l = −11→11
2522 measured reflections

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.025	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.067	Only H-atom coordinates refined
S = 1.09	w = 1/[σ^2(Fo^2) + (0.0446P)^2 + 0.0335P] where P = (Fo^2 + 2Fc^2)/3
1289 reflections	(Δ/σ)max = 0.002
190 parameters	Δρmax = 0.29 e Å^−3
3 restraints	Δρmin = −0.21 e Å^−3

Special details

Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes.

Refinement. Data were collected by measuring three sets of exposures with the detector set at 2θ = 29°, crystal-to-detector distance 5.00 cm. Refinement of F² against ALL reflections.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
O1	0.8448 (3)	1.22469 (17)	0.81811 (16)	0.0235 (3)
H5	0.928 (7)	1.258 (5)	0.915 (4)	0.035*
O2	0.9515 (2)	0.61709 (17)	0.57196 (15)	0.0203 (3)
O3	0.6661 (3)	−0.06442 (18)	0.25320 (16)	0.0209 (2)
O4	0.1441 (3)	0.35031 (18)	0.12595 (15)	0.0227 (3)
O5	0.3046 (2)	0.07138 (16)	0.01594 (14)	0.0159 (2)
N1	0.7140 (3)	0.86205 (18)	0.87460 (15)	0.0124 (2)
H1	0.642 (5)	0.742 (4)	0.873 (3)	0.019*
H2	0.618 (5)	0.948 (4)	0.949 (3)	0.019*
H3	0.889 (6)	0.908 (4)	0.906 (3)	0.019*
N2	0.4876 (3)	0.52295 (18)	0.43487 (15)	0.0126 (2)
H4	0.322 (5)	0.552 (3)	0.446 (3)	0.015*
N3	0.1800 (3)	−0.2081 (2)	0.2418 (2)	0.0210 (3)
H6	0.197 (6)	−0.326 (5)	0.200 (4)	0.025*
H7	0.007 (6)	−0.193 (4)	0.248 (3)	0.025*
C1	0.6593 (3)	0.8486 (2)	0.69714 (18)	0.0123 (3)
H11	0.454 (5)	0.844 (4)	0.680 (3)	0.015*
C2	0.8700 (3)	1.0348 (2)	0.68728 (19)	0.0165 (3)
H21	1.071 (5)	1.034 (4)	0.705 (3)	0.020*
H22	0.829 (5)	1.025 (4)	0.575 (3)	0.020*
C3	0.7128 (3)	0.6494 (2)	0.56081 (18)	0.0124 (3)
C4	0.4933 (3)	0.3171 (2)	0.30937 (17)	0.0114 (3)
H41	0.685 (5)	0.320 (3)	0.288 (3)	0.014*
C5	0.3727 (3)	0.1646 (2)	0.38577 (19)	0.0148 (3)
H51	0.473 (5)	0.216 (4)	0.494 (3)	0.018*
H52	0.163 (5)	0.152 (4)	0.394 (3)	0.018*
C6	0.4173 (3)	−0.0465 (2)	0.28399 (18)	0.0147 (3)
C7	0.3016 (3)	0.2442 (2)	0.13613 (18)	0.0131 (3)
O1W	0.4833 (3)	0.4668 (2)	0.8323 (2)	0.0290 (3)
H1W	0.585 (8)	0.384 (5)	0.831 (5)	0.044*
H2W	0.317 (8)	0.425 (5)	0.842 (5)	0.044*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
O1	0.0395 (7)	0.0113 (5)	0.0161 (5)	0.0064 (5)	−0.0041 (5)	0.0036 (4)
O2	0.0120 (5)	0.0189 (5)	0.0203 (5)	0.0066 (4)	−0.0009 (4)	−0.0010 (5)
O3	0.0167 (5)	0.0198 (5)	0.0249 (6)	0.0083 (4)	0.0014 (4)	0.0072 (5)
O4	0.0278 (6)	0.0184 (6)	0.0173 (5)	0.0123 (5)	−0.0065 (4)	0.0008 (4)
O5	0.0158 (5)	0.0141 (5)	0.0126 (4)	0.0060 (4)	−0.0004 (4)	0.0004 (4)
N1	0.0122 (5)	0.0108 (5)	0.0119 (5)	0.0023 (4)	0.0018 (4)	0.0036 (4)
N2	0.0109 (5)	0.0108 (5)	0.0121 (5)	0.0042 (4)	0.0000 (4)	0.0010 (5)
N3	0.0189 (7)	0.0128 (6)	0.0297 (7)	0.0051 (5)	0.0033 (5)	0.0080 (5)
C1	0.0120 (6)	0.0106 (6)	0.0105 (6)	0.0026 (5)	−0.0001 (5)	0.0019 (5)
C2	0.0223 (7)	0.0118 (6)	0.0122 (6)	0.0018 (5)	−0.0001 (5)	0.0043 (5)
C3	0.0111 (6)	0.0116 (6)	0.0115 (6)	0.0027 (5)	0.0017 (5)	0.0028 (5)
C4	0.0111 (6)	0.0088 (6)	0.0107 (6)	0.0028 (4)	0.0001 (5)	0.0012 (5)
C5	0.0177 (7)	0.0124 (6)	0.0128 (6)	0.0042 (5)	0.0030 (5)	0.0044 (5)
C6	0.0172 (7)	0.0140 (6)	0.0129 (6)	0.0057 (5)	−0.0003 (5)	0.0056 (5)
C7	0.0118 (6)	0.0126 (6)	0.0114 (6)	0.0025 (5)	0.0004 (5)	0.0027 (5)
O1W	0.0294 (7)	0.0166 (6)	0.0409 (8)	0.0049 (5)	0.0140 (6)	0.0137 (5)

Geometric parameters (Å, º)

O1—C2	1.4170 (19)	N3—H7	0.86 (3)
O1—H5	0.82 (3)	C1—C2	1.5320 (19)
O2—C3	1.2315 (18)	C1—C3	1.5336 (19)
O3—C6	1.2413 (19)	C1—H11	0.98 (2)
O4—C7	1.2539 (19)	C2—H21	0.97 (3)
O5—C7	1.2631 (17)	C2—H22	0.94 (3)
N1—C1	1.4955 (18)	C4—C7	1.5349 (19)
N1—H1	0.87 (3)	C4—C5	1.5436 (19)
N1—H2	0.91 (3)	C4—H41	0.93 (2)
N1—H3	0.81 (3)	C5—C6	1.516 (2)
N2—C3	1.3372 (18)	C5—H51	0.91 (3)
N2—C4	1.4587 (16)	C5—H52	0.98 (2)
N2—H4	0.86 (2)	O1W—H1W	0.88 (4)
N3—C6	1.336 (2)	O1W—H2W	0.79 (4)
N3—H6	0.83 (3)
C2—O1—H5	114 (2)	H21—C2—H22	110 (2)
C1—N1—H1	110.8 (16)	O2—C3—N2	125.02 (13)
C1—N1—H2	108.5 (15)	O2—C3—C1	119.83 (12)
H1—N1—H2	107 (2)	N2—C3—C1	115.15 (12)
C1—N1—H3	108.0 (17)	N2—C4—C7	111.01 (11)
H1—N1—H3	112 (2)	N2—C4—C5	109.02 (11)
H2—N1—H3	110 (2)	C7—C4—C5	108.53 (12)
C3—N2—C4	121.07 (12)	N2—C4—H41	109.2 (14)
C3—N2—H4	117.7 (15)	C7—C4—H41	109.1 (14)
C4—N2—H4	119.2 (15)	C5—C4—H41	110.0 (14)
C6—N3—H6	120.1 (19)	C6—C5—C4	114.41 (12)
C6—N3—H7	121.1 (18)	C6—C5—H51	105.3 (15)
H6—N3—H7	119 (3)	C4—C5—H51	108.2 (15)
N1—C1—C2	109.67 (11)	C6—C5—H52	110.2 (14)
N1—C1—C3	108.51 (12)	C4—C5—H52	108.7 (14)
C2—C1—C3	109.56 (11)	H51—C5—H52	110 (2)
N1—C1—H11	106.7 (13)	O3—C6—N3	123.02 (14)
C2—C1—H11	112.0 (13)	O3—C6—C5	120.62 (13)
C3—C1—H11	110.3 (14)	N3—C6—C5	116.19 (13)
O1—C2—C1	112.28 (12)	O4—C7—O5	124.91 (13)
O1—C2—H21	107.0 (14)	O4—C7—C4	119.34 (12)
C1—C2—H21	109.6 (14)	O5—C7—C4	115.62 (12)
O1—C2—H22	109.8 (15)	H1W—O1W—H2W	112 (3)
C1—C2—H22	108.5 (15)
N1—C1—C3—N2	124.40 (13)	C4—N2—C3—O2	8.5 (2)
C1—C3—N2—C4	−172.27 (12)	N1—C1—C3—O2	−56.29 (18)
C3—N2—C4—C7	−153.03 (13)	C2—C1—C3—O2	63.42 (17)
N2—C4—C7—O4	−7.36 (19)	C2—C1—C3—N2	−115.88 (14)
N1—C1—C2—O1	−57.08 (15)	C3—N2—C4—C5	87.47 (15)
N2—C4—C5—C6	−169.42 (11)	C7—C4—C5—C6	69.55 (15)
C4—C5—C6—O3	54.70 (19)	C5—C4—C7—O4	112.43 (15)
C4—C5—C6—N3	−129.80 (14)	N2—C4—C7—O5	176.54 (12)
C3—C1—C2—O1	−176.08 (12)	C5—C4—C7—O5	−63.66 (15)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
N1—H1···O1W	0.88 (3)	1.88 (3)	2.7446 (18)	171 (2)
N1—H2···O5^i	0.91 (3)	1.92 (3)	2.7712 (16)	156 (2)
N1—H3···O5^ii	0.81 (3)	2.03 (3)	2.8037 (17)	169 (2)
N2—H4···O2^iii	0.86 (2)	2.12 (2)	2.9349 (16)	156 (2)
O1—H5···O4^ii	0.81 (3)	1.82 (3)	2.6418 (16)	174 (3)
C1—H11···O2^iii	0.98 (2)	2.45 (2)	3.2908 (18)	144.5 (18)
N3—H6···O4^iv	0.82 (3)	2.17 (3)	2.9784 (18)	165 (3)
N3—H7···O3^iii	0.86 (2)	2.08 (3)	2.9014 (19)	160 (3)
C5—H52···O3^iii	0.98 (2)	2.44 (2)	3.2899 (19)	144.2 (19)
O1W—H1W···O1^iv	0.88 (4)	1.90 (4)	2.775 (2)	173 (3)
O1W—H2W···O1^v	0.78 (4)	2.31 (4)	3.081 (2)	165 (3)

Symmetry codes: (i) x, y+1, z+1; (ii) x+1, y+1, z+1; (iii) x−1, y, z; (iv) x, y−1, z; (v) x−1, y−1, z.

(SY) L-Seryl-L-tyrosine monohydrate

Crystal data

C12H16N2O5·H2O	Dx = 1.452 Mg m^−3
Mr = 286.28	Mo Kα radiation, λ = 0.71073 Å
Orthorhombic, P21212	Cell parameters from 8269 reflections
a = 15.3480 (9) Å	θ = 1.8–28.4°
b = 17.8805 (11) Å	µ = 0.12 mm^−1
c = 4.7728 (3) Å	T = 105 K
V = 1309.80 (14) Å^3	Block, colourless
Z = 4	0.80 × 0.50 × 0.20 mm
F(000) = 608

Data collection

Siemens SMART CCD diffractometer	1932 independent reflections
Radiation source: fine-focus sealed tube	1655 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.040
Detector resolution: 8.3 pixels mm^-1	θmax = 28.4°, θmin = 1.8°
Sets of exposures each taken over 0.3° ω rotation scans	h = −20→20
Absorption correction: multi-scan (SADABS; Sheldrick, 1996)	k = −23→23
Tmin = 0.814, Tmax = 0.976	l = −6→6
14151 measured reflections

Refinement

Refinement on F^2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F^2 > 2σ(F^2)] = 0.038	H atoms treated by a mixture of independent and constrained refinement
wR(F^2) = 0.102	w = 1/[σ^2(Fo^2) + (0.0385P)^2 + 0.6547P] where P = (Fo^2 + 2Fc^2)/3
S = 1.14	(Δ/σ)max = 0.001
1932 reflections	Δρmax = 0.24 e Å^−3
206 parameters	Δρmin = −0.24 e Å^−3
3 restraints	Extinction correction: SHELXL97, Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.025 (3)

Special details

Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes.

Refinement. Data were collected by measuring three sets of exposures with the detector set at 2θ = 29°, crystal-to-detector distance 5.00 cm. Refinement of F² against ALL reflections.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
O1	0.09778 (12)	0.52864 (10)	0.1718 (4)	0.0313 (4)
H4	0.048 (2)	0.5513 (18)	0.090 (8)	0.047*
O2	0.27723 (13)	0.58953 (11)	0.9110 (4)	0.0322 (5)
O3	0.70144 (12)	0.61764 (11)	−0.0543 (5)	0.0393 (5)
H6	0.735 (2)	0.655 (2)	−0.104 (9)	0.059*
O4	0.30283 (12)	0.77640 (10)	0.2429 (4)	0.0299 (4)
O5	0.38375 (11)	0.84101 (9)	0.5464 (4)	0.0274 (4)
N1	0.19134 (15)	0.47846 (12)	0.6692 (5)	0.0249 (4)
H1	0.154 (2)	0.4957 (18)	0.825 (7)	0.037*
H2	0.159 (2)	0.4404 (17)	0.560 (7)	0.037*
H3	0.241 (2)	0.4547 (17)	0.748 (7)	0.037*
N2	0.31198 (14)	0.64926 (12)	0.5087 (4)	0.0236 (4)
H5	0.3047 (18)	0.6492 (17)	0.337 (7)	0.028*
C1	0.21854 (15)	0.54057 (13)	0.4828 (5)	0.0227 (5)
H11	0.2549	0.5201	0.3268	0.027*
C2	0.13860 (16)	0.57872 (13)	0.3612 (6)	0.0260 (5)
H21	0.0977	0.5923	0.5133	0.031*
H22	0.1559	0.6250	0.2621	0.031*
C3	0.27301 (16)	0.59550 (14)	0.6552 (5)	0.0231 (5)
C4	0.35316 (16)	0.71277 (13)	0.6492 (5)	0.0225 (5)
H41	0.3173	0.7235	0.8194	0.027*
C5	0.44587 (15)	0.69475 (13)	0.7543 (6)	0.0240 (5)
H51	0.4679	0.7386	0.8592	0.029*
H52	0.4421	0.6525	0.8878	0.029*
C6	0.51152 (15)	0.67495 (13)	0.5316 (5)	0.0234 (5)
C7	0.52259 (16)	0.60151 (13)	0.4421 (6)	0.0278 (5)
H71	0.4866	0.5634	0.5183	0.033*
C8	0.58528 (16)	0.58270 (14)	0.2429 (7)	0.0311 (6)
H81	0.5914	0.5324	0.1821	0.037*
C9	0.63865 (16)	0.63806 (14)	0.1344 (6)	0.0273 (5)
C10	0.62790 (15)	0.71177 (14)	0.2176 (6)	0.0274 (5)
H101	0.6633	0.7500	0.1396	0.033*
C11	0.56504 (15)	0.72919 (14)	0.4154 (6)	0.0260 (5)
H111	0.5584	0.7797	0.4731	0.031*
C12	0.34644 (15)	0.78185 (13)	0.4617 (5)	0.0235 (5)
O1W	0.47158 (13)	0.88314 (12)	1.0312 (4)	0.0365 (5)
H1W	0.452 (2)	0.865 (2)	1.181 (5)	0.055*
H2W	0.436 (2)	0.868 (2)	0.902 (5)	0.055*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
O1	0.0277 (9)	0.0286 (9)	0.0375 (11)	−0.0001 (7)	−0.0083 (8)	−0.0052 (8)
O2	0.0424 (10)	0.0338 (10)	0.0204 (9)	−0.0107 (9)	−0.0011 (8)	0.0022 (8)
O3	0.0364 (10)	0.0276 (9)	0.0539 (13)	−0.0026 (8)	0.0198 (10)	−0.0065 (10)
O4	0.0378 (9)	0.0303 (9)	0.0217 (8)	0.0038 (8)	−0.0059 (8)	−0.0004 (8)
O5	0.0317 (9)	0.0229 (8)	0.0276 (9)	−0.0036 (7)	−0.0024 (8)	0.0014 (8)
N1	0.0270 (10)	0.0234 (10)	0.0243 (10)	−0.0020 (9)	−0.0030 (9)	0.0010 (9)
N2	0.0285 (10)	0.0262 (9)	0.0162 (9)	−0.0054 (8)	−0.0016 (9)	0.0007 (9)
C1	0.0246 (10)	0.0221 (10)	0.0214 (11)	−0.0029 (9)	−0.0007 (10)	0.0003 (9)
C2	0.0274 (12)	0.0227 (11)	0.0279 (12)	0.0024 (10)	−0.0026 (10)	−0.0020 (10)
C3	0.0219 (11)	0.0256 (11)	0.0219 (10)	−0.0010 (10)	−0.0002 (9)	0.0003 (10)
C4	0.0244 (11)	0.0239 (11)	0.0193 (10)	−0.0027 (9)	−0.0001 (9)	−0.0006 (10)
C5	0.0253 (11)	0.0252 (11)	0.0214 (10)	−0.0003 (9)	−0.0025 (10)	0.0006 (10)
C6	0.0214 (10)	0.0240 (11)	0.0247 (11)	0.0019 (9)	−0.0011 (10)	0.0002 (10)
C7	0.0274 (12)	0.0227 (11)	0.0332 (13)	−0.0028 (9)	0.0030 (11)	−0.0002 (11)
C8	0.0304 (12)	0.0241 (11)	0.0388 (14)	−0.0012 (10)	0.0049 (12)	−0.0028 (12)
C9	0.0231 (11)	0.0269 (12)	0.0319 (13)	0.0018 (9)	0.0030 (10)	−0.0023 (11)
C10	0.0223 (11)	0.0246 (11)	0.0352 (14)	−0.0032 (9)	0.0013 (11)	−0.0002 (11)
C11	0.0241 (11)	0.0232 (11)	0.0306 (13)	−0.0017 (9)	0.0000 (11)	−0.0019 (10)
C12	0.0234 (11)	0.0244 (11)	0.0226 (11)	0.0011 (9)	0.0016 (10)	−0.0027 (10)
O1W	0.0410 (11)	0.0398 (11)	0.0288 (10)	−0.0130 (9)	−0.0016 (9)	0.0059 (9)

Geometric parameters (Å, º)

O1—C2	1.418 (3)	C4—C12	1.529 (3)
O1—H4	0.95 (3)	C4—C5	1.543 (3)
O2—C3	1.227 (3)	C4—H41	1.0000
O3—C9	1.369 (3)	C5—C6	1.507 (3)
O3—H6	0.87 (4)	C5—H51	0.9900
O4—C12	1.244 (3)	C5—H52	0.9900
O5—C12	1.269 (3)	C6—C11	1.387 (3)
N1—C1	1.483 (3)	C6—C7	1.391 (3)
N1—H1	0.99 (3)	C7—C8	1.394 (4)
N1—H2	0.99 (3)	C7—H71	0.9500
N1—H3	0.95 (3)	C8—C9	1.385 (4)
N2—C3	1.331 (3)	C8—H81	0.9500
N2—C4	1.462 (3)	C9—C10	1.386 (3)
N2—H5	0.82 (3)	C10—C11	1.385 (4)
C1—C2	1.519 (3)	C10—H101	0.9500
C1—C3	1.530 (3)	C11—H111	0.9500
C1—H11	1.0000	O1W—H1W	0.846 (18)
C2—H21	0.9900	O1W—H2W	0.864 (17)
C2—H22	0.9900
C2—O1—H4	110 (2)	C12—C4—H41	106.5
C9—O3—H6	113 (3)	C5—C4—H41	106.5
C1—N1—H1	112.4 (19)	C6—C5—C4	115.9 (2)
C1—N1—H2	110.0 (19)	C6—C5—H51	108.3
H1—N1—H2	109 (2)	C4—C5—H51	108.3
C1—N1—H3	110.2 (19)	C6—C5—H52	108.3
H1—N1—H3	108 (3)	C4—C5—H52	108.3
H2—N1—H3	108 (2)	H51—C5—H52	107.4
C3—N2—C4	120.9 (2)	C11—C6—C7	117.7 (2)
C3—N2—H5	117 (2)	C11—C6—C5	120.9 (2)
C4—N2—H5	121 (2)	C7—C6—C5	121.3 (2)
N1—C1—C2	109.77 (19)	C6—C7—C8	121.4 (2)
N1—C1—C3	108.2 (2)	C6—C7—H71	119.3
C2—C1—C3	111.01 (19)	C8—C7—H71	119.3
N1—C1—H11	109.3	C9—C8—C7	119.4 (2)
C2—C1—H11	109.3	C9—C8—H81	120.3
C3—C1—H11	109.3	C7—C8—H81	120.3
O1—C2—C1	108.47 (19)	O3—C9—C8	118.1 (2)
O1—C2—H21	110.0	O3—C9—C10	121.7 (2)
C1—C2—H21	110.0	C8—C9—C10	120.1 (2)
O1—C2—H22	110.0	C11—C10—C9	119.5 (2)
C1—C2—H22	110.0	C11—C10—H101	120.3
H21—C2—H22	108.4	C9—C10—H101	120.3
O2—C3—N2	124.2 (2)	C10—C11—C6	121.9 (2)
O2—C3—C1	120.5 (2)	C10—C11—H111	119.1
N2—C3—C1	115.3 (2)	C6—C11—H111	119.1
N2—C4—C12	109.3 (2)	O4—C12—O5	125.1 (2)
N2—C4—C5	112.7 (2)	O4—C12—C4	117.7 (2)
C12—C4—C5	114.92 (19)	O5—C12—C4	117.1 (2)
N2—C4—H41	106.5	H1W—O1W—H2W	105 (2)
N1—C1—C3—N2	171.4 (2)	C4—C5—C6—C11	93.4 (3)
C1—C3—N2—C4	169.2 (2)	C11—C6—C7—C8	0.1 (4)
C3—N2—C4—C12	−148.6 (2)	C5—C6—C7—C8	−177.8 (2)
N2—C4—C12—O4	6.1 (3)	C6—C7—C8—C9	0.9 (4)
N1—C1—C2—O1	−68.9 (3)	C7—C8—C9—O3	178.0 (3)
N2—C4—C5—C6	62.4 (3)	C7—C8—C9—C10	−1.9 (4)
C4—C5—C6—C7	−88.7 (3)	O3—C9—C10—C11	−178.1 (2)
C3—C1—C2—O1	171.6 (2)	C8—C9—C10—C11	1.8 (4)
C4—N2—C3—O2	−9.2 (4)	C9—C10—C11—C6	−0.7 (4)
N1—C1—C3—O2	−10.1 (3)	C7—C6—C11—C10	−0.2 (4)
C2—C1—C3—O2	110.4 (3)	C5—C6—C11—C10	177.7 (2)
C2—C1—C3—N2	−68.1 (3)	C5—C4—C12—O4	133.9 (2)
C3—N2—C4—C5	82.3 (3)	N2—C4—C12—O5	−176.0 (2)
C12—C4—C5—C6	−63.7 (3)	C5—C4—C12—O5	−48.2 (3)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
N1—H1···O1^i	0.99 (3)	1.96 (3)	2.936 (3)	171 (3)
N1—H2···O5^ii	0.99 (3)	1.96 (3)	2.903 (3)	158 (3)
N1—H3···O3^iii	0.95 (3)	1.83 (3)	2.721 (3)	155 (3)
O1—H4···O1W^iv	0.95 (3)	1.76 (3)	2.679 (3)	163 (3)
N2—H5···O2^v	0.82 (3)	2.34 (3)	3.092 (3)	153 (3)
O3—H6···O4^vi	0.87 (4)	1.74 (4)	2.612 (3)	173 (4)
C1—H11···O2^v	1.00	2.37	3.004 (3)	121
O1W—H1W···O5^i	0.85 (2)	2.07 (2)	2.904 (3)	167 (4)
O1W—H2W···O5	0.85 (2)	1.94 (2)	2.782 (3)	164 (3)

Symmetry codes: (i) x, y, z+1; (ii) −x+1/2, y−1/2, −z+1; (iii) −x+1, −y+1, z+1; (iv) x−1/2, −y+3/2, −z+1; (v) x, y, z−1; (vi) x+1/2, −y+3/2, −z.

(WS) L-Tryptophanyl-L-serine monohydrate

Crystal data

C14H17N3O4·H2O	F(000) = 328
Mr = 309.32	Dx = 1.399 Mg m^−3
Monoclinic, P21	Mo Kα radiation, λ = 0.71073 Å
a = 6.5613 (5) Å	Cell parameters from 3410 reflections
b = 9.1474 (7) Å	θ = 1.7–27.9°
c = 12.5052 (9) Å	µ = 0.11 mm^−1
β = 101.973 (1)°	T = 105 K
V = 734.22 (10) Å^3	Plate, colourless
Z = 2	0.40 × 0.25 × 0.08 mm

Data collection

Siemens SMART CCD diffractometer	1827 independent reflections
Radiation source: fine-focus sealed tube	1623 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.073
Detector resolution: 8.3 pixels mm^-1	θmax = 27.9°, θmin = 1.7°
Sets of exposures each taken over 0.3° ω rotation scans	h = −8→8
Absorption correction: multi-scan (SADABS; Sheldrick, 1996)	k = −7→12
Tmin = 0.893, Tmax = 0.991	l = −14→16
4829 measured reflections

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.036	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.091	H atoms treated by a mixture of independent and constrained refinement
S = 1.04	w = 1/[σ^2(Fo^2) + (0.0493P)^2 + 0.0424P] where P = (Fo^2 + 2Fc^2)/3
1827 reflections	(Δ/σ)max = 0.004
225 parameters	Δρmax = 0.21 e Å^−3
1 restraint	Δρmin = −0.25 e Å^−3

Special details

Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes.

Refinement. Data were collected by measuring three sets of exposures with the detector set at 2θ = 29°, crystal-to-detector distance 5.00 cm. Refinement of F² against ALL reflections.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
O1	0.4006 (3)	0.57631 (17)	0.26300 (12)	0.0216 (4)
O2	0.0728 (3)	0.78297 (18)	−0.01045 (13)	0.0229 (4)
H6	0.166 (5)	0.713 (3)	−0.021 (2)	0.034*
O3	−0.3112 (3)	0.56471 (17)	0.07650 (14)	0.0228 (4)
O4	−0.3174 (3)	0.80483 (17)	0.10278 (13)	0.0230 (4)
N1	0.5801 (3)	0.3416 (2)	0.19792 (16)	0.0195 (4)
H1	0.625 (5)	0.351 (3)	0.271 (2)	0.029*
H2	0.630 (5)	0.410 (3)	0.162 (2)	0.029*
H3	0.634 (5)	0.253 (4)	0.177 (2)	0.029*
N2	0.4865 (4)	0.2155 (2)	0.53366 (17)	0.0290 (5)
H4	0.563 (5)	0.171 (4)	0.590 (3)	0.035*
N3	0.0926 (3)	0.53940 (19)	0.14458 (15)	0.0167 (4)
H5	0.018 (5)	0.481 (3)	0.101 (2)	0.020*
C1	0.3489 (3)	0.3458 (2)	0.17062 (16)	0.0165 (4)
H11	0.2991	0.3260	0.0908	0.020*
C2	0.2631 (4)	0.2273 (2)	0.23731 (18)	0.0195 (5)
H21	0.1092	0.2270	0.2154	0.023*
H22	0.3132	0.1307	0.2181	0.023*
C3	0.3227 (4)	0.2460 (2)	0.35877 (18)	0.0202 (5)
C4	0.4870 (4)	0.1794 (3)	0.42754 (19)	0.0254 (5)
H41	0.5862	0.1175	0.4048	0.030*
C5	0.2135 (4)	0.3274 (2)	0.42683 (18)	0.0201 (4)
C6	0.3178 (4)	0.3028 (2)	0.53607 (19)	0.0242 (5)
C7	0.2445 (5)	0.3570 (3)	0.6254 (2)	0.0329 (6)
H71	0.3154	0.3380	0.6983	0.039*
C8	0.0648 (5)	0.4393 (3)	0.6031 (2)	0.0386 (7)
H81	0.0096	0.4764	0.6621	0.046*
C9	−0.0384 (5)	0.4696 (3)	0.4960 (3)	0.0371 (7)
H91	−0.1605	0.5282	0.4836	0.044*
C10	0.0348 (4)	0.4153 (3)	0.4078 (2)	0.0270 (6)
H101	−0.0352	0.4375	0.3353	0.032*
C11	0.2825 (4)	0.4997 (2)	0.19674 (16)	0.0162 (4)
C12	0.0082 (4)	0.6832 (2)	0.15927 (17)	0.0182 (5)
H121	0.0299	0.7043	0.2393	0.022*
C13	0.1183 (4)	0.8015 (2)	0.10535 (18)	0.0207 (5)
H131	0.0712	0.8993	0.1240	0.025*
H132	0.2707	0.7951	0.1334	0.025*
C14	−0.2266 (4)	0.6854 (2)	0.10997 (17)	0.0176 (4)
O1W	0.6546 (3)	0.09657 (19)	0.08266 (15)	0.0237 (4)
H1W	0.684 (6)	0.009 (5)	0.099 (3)	0.050 (11)*
H2W	0.545 (6)	0.096 (4)	0.030 (3)	0.048 (10)*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
O1	0.0246 (9)	0.0180 (8)	0.0197 (7)	0.0008 (7)	−0.0009 (6)	−0.0045 (6)
O2	0.0251 (9)	0.0205 (8)	0.0229 (8)	0.0047 (7)	0.0047 (7)	0.0066 (6)
O3	0.0208 (9)	0.0166 (8)	0.0295 (8)	−0.0021 (7)	0.0018 (7)	0.0002 (6)
O4	0.0243 (9)	0.0161 (8)	0.0283 (8)	0.0054 (7)	0.0047 (7)	0.0024 (6)
N1	0.0206 (10)	0.0150 (9)	0.0229 (9)	0.0014 (8)	0.0042 (8)	0.0001 (8)
N2	0.0296 (13)	0.0306 (12)	0.0241 (10)	0.0023 (10)	−0.0007 (9)	0.0121 (9)
N3	0.0192 (10)	0.0118 (9)	0.0179 (9)	0.0002 (7)	0.0010 (7)	−0.0004 (7)
C1	0.0195 (11)	0.0124 (9)	0.0164 (9)	0.0011 (9)	0.0004 (8)	0.0002 (8)
C2	0.0226 (12)	0.0140 (10)	0.0215 (10)	−0.0007 (9)	0.0033 (9)	0.0010 (8)
C3	0.0225 (12)	0.0147 (10)	0.0232 (11)	0.0000 (9)	0.0046 (9)	0.0060 (9)
C4	0.0254 (13)	0.0237 (11)	0.0276 (12)	0.0058 (11)	0.0067 (10)	0.0082 (10)
C5	0.0229 (11)	0.0150 (9)	0.0223 (10)	−0.0027 (9)	0.0047 (9)	0.0018 (8)
C6	0.0308 (13)	0.0186 (11)	0.0230 (11)	−0.0069 (10)	0.0051 (10)	0.0038 (8)
C7	0.0519 (18)	0.0265 (13)	0.0223 (11)	−0.0105 (13)	0.0126 (11)	0.0002 (10)
C8	0.059 (2)	0.0255 (13)	0.0400 (16)	−0.0023 (14)	0.0305 (14)	−0.0032 (11)
C9	0.0411 (17)	0.0257 (14)	0.0514 (16)	0.0069 (12)	0.0256 (14)	0.0030 (12)
C10	0.0281 (14)	0.0224 (12)	0.0317 (13)	0.0011 (10)	0.0091 (10)	0.0052 (10)
C11	0.0210 (11)	0.0131 (10)	0.0142 (9)	0.0001 (9)	0.0027 (8)	0.0007 (8)
C12	0.0224 (12)	0.0126 (9)	0.0187 (10)	0.0015 (9)	0.0017 (9)	0.0001 (8)
C13	0.0205 (11)	0.0136 (10)	0.0265 (11)	−0.0008 (9)	0.0014 (9)	0.0005 (8)
C14	0.0204 (11)	0.0152 (9)	0.0176 (10)	0.0011 (9)	0.0047 (8)	0.0024 (8)
O1W	0.0258 (10)	0.0156 (8)	0.0284 (9)	0.0019 (7)	0.0025 (8)	−0.0011 (7)

Geometric parameters (Å, º)

O1—C11	1.229 (3)	C3—C4	1.374 (3)
O2—C13	1.427 (3)	C3—C5	1.430 (3)
O2—H6	0.91 (3)	C4—H41	0.9500
O3—C14	1.268 (3)	C5—C10	1.401 (4)
O4—C14	1.238 (3)	C5—C6	1.413 (3)
N1—C1	1.485 (3)	C6—C7	1.395 (4)
N1—H1	0.90 (3)	C7—C8	1.378 (5)
N1—H2	0.87 (3)	C7—H71	0.9500
N1—H3	0.94 (4)	C8—C9	1.397 (4)
N2—C4	1.368 (3)	C8—H81	0.9500
N2—C6	1.370 (3)	C9—C10	1.383 (4)
N2—H4	0.87 (3)	C9—H91	0.9500
N3—C11	1.331 (3)	C10—H101	0.9500
N3—C12	1.454 (3)	C12—C13	1.532 (3)
N3—H5	0.84 (3)	C12—C14	1.536 (3)
C1—C11	1.529 (3)	C12—H121	1.0000
C1—C2	1.543 (3)	C13—H131	0.9900
C1—H11	1.0000	C13—H132	0.9900
C2—C3	1.497 (3)	O1W—H1W	0.84 (4)
C2—H21	0.9900	O1W—H2W	0.87 (4)
C2—H22	0.9900
C13—O2—H6	103.2 (19)	N2—C6—C7	129.7 (2)
C1—N1—H1	109.5 (19)	N2—C6—C5	107.6 (2)
C1—N1—H2	110 (2)	C7—C6—C5	122.6 (2)
H1—N1—H2	112 (3)	C8—C7—C6	117.1 (2)
C1—N1—H3	112.4 (19)	C8—C7—H71	121.5
H1—N1—H3	107 (3)	C6—C7—H71	121.5
H2—N1—H3	106 (2)	C7—C8—C9	121.7 (3)
C4—N2—C6	109.0 (2)	C7—C8—H81	119.1
C4—N2—H4	123 (2)	C9—C8—H81	119.1
C6—N2—H4	126 (2)	C10—C9—C8	120.9 (3)
C11—N3—C12	121.82 (19)	C10—C9—H91	119.5
C11—N3—H5	120.2 (19)	C8—C9—H91	119.5
C12—N3—H5	117.9 (19)	C9—C10—C5	119.2 (2)
N1—C1—C11	107.31 (18)	C9—C10—H101	120.4
N1—C1—C2	109.11 (17)	C5—C10—H101	120.4
C11—C1—C2	112.27 (18)	O1—C11—N3	124.7 (2)
N1—C1—H11	109.4	O1—C11—C1	120.07 (19)
C11—C1—H11	109.4	N3—C11—C1	115.18 (18)
C2—C1—H11	109.4	N3—C12—C13	110.88 (19)
C3—C2—C1	114.85 (18)	N3—C12—C14	109.74 (18)
C3—C2—H21	108.6	C13—C12—C14	109.83 (17)
C1—C2—H21	108.6	N3—C12—H121	108.8
C3—C2—H22	108.6	C13—C12—H121	108.8
C1—C2—H22	108.6	C14—C12—H121	108.8
H21—C2—H22	107.5	O2—C13—C12	110.14 (17)
C4—C3—C5	106.4 (2)	O2—C13—H131	109.6
C4—C3—C2	126.2 (2)	C12—C13—H131	109.6
C5—C3—C2	127.2 (2)	O2—C13—H132	109.6
N2—C4—C3	109.9 (2)	C12—C13—H132	109.6
N2—C4—H41	125.0	H131—C13—H132	108.1
C3—C4—H41	125.0	O4—C14—O3	125.0 (2)
C10—C5—C6	118.4 (2)	O4—C14—C12	117.9 (2)
C10—C5—C3	134.7 (2)	O3—C14—C12	117.1 (2)
C6—C5—C3	106.9 (2)	H1W—O1W—H2W	107 (3)
N1—C1—C11—N3	157.96 (19)	C3—C5—C6—N2	2.3 (3)
C1—C11—N3—C12	−178.97 (19)	C10—C5—C6—C7	3.0 (4)
C11—N3—C12—C14	−167.49 (19)	C3—C5—C6—C7	−175.2 (2)
N3—C12—C14—O3	7.1 (3)	N2—C6—C7—C8	−177.9 (3)
N1—C1—C2—C3	61.6 (3)	C5—C6—C7—C8	−1.1 (4)
C1—C2—C3—C4	−95.8 (3)	C6—C7—C8—C9	−1.0 (4)
N3—C12—C13—O2	66.3 (2)	C7—C8—C9—C10	1.2 (5)
C11—C1—C2—C3	−57.2 (3)	C8—C9—C10—C5	0.8 (4)
C1—C2—C3—C5	88.9 (3)	C6—C5—C10—C9	−2.8 (4)
C6—N2—C4—C3	1.8 (3)	C3—C5—C10—C9	174.7 (3)
C5—C3—C4—N2	−0.4 (3)	C12—N3—C11—O1	2.1 (3)
C2—C3—C4—N2	−176.5 (2)	N1—C1—C11—O1	−23.0 (3)
C4—C3—C5—C10	−178.9 (3)	C2—C1—C11—O1	96.9 (2)
C2—C3—C5—C10	−2.8 (4)	C2—C1—C11—N3	−82.2 (2)
C4—C3—C5—C6	−1.2 (3)	C11—N3—C12—C13	71.0 (3)
C2—C3—C5—C6	174.9 (2)	C14—C12—C13—O2	−55.2 (2)
C4—N2—C6—C7	174.6 (2)	N3—C12—C14—O4	−170.76 (19)
C4—N2—C6—C5	−2.5 (3)	C13—C12—C14—O4	−48.6 (3)
C10—C5—C6—N2	−179.6 (2)	C13—C12—C14—O3	129.2 (2)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
N1—H1···C3	0.90 (3)	2.64 (3)	3.012 (3)	106 (2)
N1—H2···O3^i	0.87 (3)	1.86 (3)	2.726 (3)	170 (3)
N1—H3···O1W	0.94 (4)	1.88 (3)	2.762 (3)	156 (3)
N2—H4···O1^ii	0.87 (3)	2.01 (3)	2.802 (3)	151 (3)
N3—H5···O2^iii	0.84 (3)	2.16 (3)	2.956 (2)	159 (3)
O2—H6···O1W^iv	0.91 (3)	1.87 (3)	2.756 (3)	164 (3)
C1—H11···O2^iii	1.00	2.47	3.114 (3)	122
C1—H11···O4^iii	1.00	2.46	3.403 (3)	158
C9—H91···C6^v	0.95	2.71	3.537 (4)	146
O1W—H1W···O4^vi	0.84 (4)	1.87 (4)	2.683 (2)	164 (4)
O1W—H2W···O3^iii	0.87 (4)	1.83 (4)	2.694 (2)	171 (4)

Symmetry codes: (i) x+1, y, z; (ii) −x+1, y−1/2, −z+1; (iii) −x, y−1/2, −z; (iv) −x+1, y+1/2, −z; (v) −x, y+1/2, −z+1; (vi) x+1, y−1, z.

(YW) L-tyrosyl-L-tryptophane monohydrate

Crystal data

C20H21N3O4·H2O	F(000) = 408
Mr = 385.41	Dx = 1.428 Mg m^−3
Monoclinic, P21	Mo Kα radiation, λ = 0.71073 Å
a = 5.7309 (3) Å	Cell parameters from 3908 reflections
b = 8.1960 (4) Å	θ = 2.1–27.9°
c = 19.0952 (9) Å	µ = 0.10 mm^−1
β = 91.694 (1)°	T = 105 K
V = 896.52 (8) Å^3	Block, yellow
Z = 2	0.36 × 0.20 × 0.14 mm

Data collection

Siemens SMART CCD diffractometer	2245 independent reflections
Radiation source: fine-focus sealed tube	2089 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.045
Detector resolution: 8.3 pixels mm^-1	θmax = 27.9°, θmin = 2.1°
Sets of exposures each taken over 0.3° ω rotation scans	h = −6→7
Absorption correction: multi-scan (SADABS; Sheldrick, 1996)	k = −6→10
Tmin = 0.882, Tmax = 0.986	l = −25→22
5858 measured reflections

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.031	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.080	H atoms treated by a mixture of independent and constrained refinement
S = 1.02	w = 1/[σ^2(Fo^2) + (0.0483P)^2 + 0.1067P] where P = (Fo^2 + 2Fc^2)/3
2245 reflections	(Δ/σ)max = 0.002
284 parameters	Δρmax = 0.22 e Å^−3
4 restraints	Δρmin = −0.17 e Å^−3

Special details

Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes.

Refinement. Data were collected by measuring three sets of exposures with the detector set at 2θ = 29°, crystal-to-detector distance 5.00 cm. Refinement of F² against ALL reflections.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
O1	0.4999 (3)	0.4479 (2)	0.38676 (8)	0.0250 (3)
H4	0.451 (5)	0.513 (4)	0.3542 (14)	0.038*
O2	0.4612 (2)	0.60015 (18)	0.70704 (7)	0.0198 (3)
O3	0.8189 (2)	0.25717 (19)	0.77450 (7)	0.0194 (3)
O4	0.5038 (2)	0.17317 (19)	0.71301 (7)	0.0199 (3)
N1	0.0973 (3)	0.7550 (2)	0.65267 (9)	0.0196 (3)
H1	0.256 (5)	0.760 (4)	0.6403 (13)	0.029*
H2	0.084 (5)	0.847 (4)	0.6856 (13)	0.029*
H3	0.015 (4)	0.771 (4)	0.6140 (14)	0.029*
N2	0.2481 (3)	0.4263 (2)	0.77238 (8)	0.0147 (3)
H5	0.114 (4)	0.379 (3)	0.7782 (11)	0.018*
N3	−0.0105 (3)	0.4665 (2)	0.99236 (9)	0.0246 (4)
H6	−0.134 (5)	0.527 (4)	0.9999 (13)	0.030*
C1	0.0442 (3)	0.5953 (2)	0.68609 (9)	0.0157 (3)
H11	−0.0778	0.6118	0.7218	0.019*
C2	−0.0460 (3)	0.4717 (2)	0.63084 (9)	0.0175 (4)
H21	−0.0493	0.3620	0.6525	0.021*
H22	−0.2083	0.5008	0.6167	0.021*
C3	0.0991 (3)	0.4636 (2)	0.56578 (9)	0.0154 (4)
C4	0.3102 (3)	0.3784 (2)	0.56479 (9)	0.0168 (4)
H41	0.3648	0.3227	0.6057	0.020*
C5	0.4418 (3)	0.3741 (2)	0.50454 (10)	0.0183 (4)
H51	0.5841	0.3146	0.5044	0.022*
C6	0.3644 (3)	0.4572 (2)	0.44429 (9)	0.0174 (4)
C7	0.1542 (3)	0.5420 (2)	0.44429 (9)	0.0177 (4)
H71	0.1001	0.5982	0.4035	0.021*
C8	0.0235 (3)	0.5438 (2)	0.50473 (10)	0.0175 (4)
H81	−0.1207	0.6010	0.5043	0.021*
C9	0.2728 (3)	0.5405 (2)	0.72320 (9)	0.0146 (3)
C10	0.4526 (3)	0.3582 (2)	0.80947 (9)	0.0150 (4)
H101	0.5493	0.4499	0.8291	0.018*
C11	0.3781 (3)	0.2478 (3)	0.87026 (9)	0.0174 (4)
H111	0.528 (4)	0.198 (3)	0.8893 (12)	0.021*
H112	0.285 (4)	0.158 (4)	0.8493 (13)	0.026 (6)*
C12	0.2526 (3)	0.3307 (2)	0.92882 (9)	0.0181 (4)
C13	0.0498 (3)	0.4194 (3)	0.92593 (10)	0.0233 (4)
H131	−0.0369	0.4448	0.8842	0.028*
C14	0.3228 (3)	0.3214 (2)	1.00197 (9)	0.0169 (4)
C15	0.5110 (3)	0.2497 (3)	1.03895 (10)	0.0205 (4)
H151	0.6287	0.1929	1.0148	0.025*
C16	0.5227 (4)	0.2632 (3)	1.11160 (10)	0.0244 (4)
H161	0.6512	0.2165	1.1370	0.029*
C17	0.3480 (4)	0.3444 (3)	1.14817 (10)	0.0259 (4)
H171	0.3589	0.3496	1.1979	0.031*
C18	0.1606 (4)	0.4170 (3)	1.11315 (10)	0.0241 (4)
H181	0.0427	0.4723	1.1378	0.029*
C19	0.1514 (3)	0.4058 (2)	1.04015 (10)	0.0194 (4)
C20	0.6037 (3)	0.2555 (2)	0.76074 (9)	0.0147 (3)
O1W	0.0885 (3)	0.0181 (2)	0.72966 (9)	0.0277 (3)
H1W	0.215 (3)	0.070 (4)	0.7244 (15)	0.042*
H2W	−0.011 (4)	0.090 (3)	0.7413 (15)	0.042*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
O1	0.0322 (8)	0.0244 (8)	0.0191 (7)	0.0070 (7)	0.0115 (6)	0.0060 (6)
O2	0.0167 (6)	0.0223 (7)	0.0206 (7)	−0.0022 (6)	0.0023 (5)	0.0017 (6)
O3	0.0144 (6)	0.0213 (6)	0.0226 (6)	−0.0009 (6)	0.0024 (5)	−0.0008 (6)
O4	0.0192 (6)	0.0242 (7)	0.0163 (6)	0.0000 (6)	0.0011 (5)	−0.0046 (6)
N1	0.0240 (8)	0.0179 (8)	0.0168 (7)	0.0015 (8)	0.0002 (6)	0.0008 (7)
N2	0.0128 (7)	0.0158 (7)	0.0156 (7)	0.0001 (6)	0.0007 (5)	0.0007 (6)
N3	0.0209 (8)	0.0332 (10)	0.0201 (8)	0.0072 (8)	0.0047 (6)	−0.0018 (8)
C1	0.0160 (8)	0.0176 (8)	0.0136 (8)	0.0015 (7)	0.0022 (6)	0.0007 (7)
C2	0.0165 (8)	0.0206 (9)	0.0154 (8)	−0.0029 (7)	0.0015 (7)	−0.0005 (8)
C3	0.0168 (8)	0.0155 (8)	0.0139 (8)	−0.0023 (7)	−0.0001 (6)	−0.0020 (7)
C4	0.0192 (8)	0.0171 (9)	0.0139 (8)	−0.0015 (8)	−0.0013 (7)	0.0013 (7)
C5	0.0182 (9)	0.0165 (8)	0.0202 (9)	0.0010 (7)	0.0015 (7)	−0.0008 (7)
C6	0.0212 (9)	0.0150 (8)	0.0162 (8)	−0.0029 (7)	0.0041 (7)	−0.0011 (7)
C7	0.0224 (9)	0.0173 (9)	0.0132 (8)	−0.0004 (7)	−0.0011 (7)	0.0018 (7)
C8	0.0168 (8)	0.0173 (9)	0.0182 (8)	0.0001 (7)	−0.0016 (7)	−0.0010 (8)
C9	0.0165 (8)	0.0151 (8)	0.0123 (8)	0.0011 (7)	0.0017 (6)	−0.0033 (7)
C10	0.0145 (8)	0.0161 (9)	0.0144 (8)	0.0005 (7)	0.0009 (6)	−0.0013 (7)
C11	0.0203 (8)	0.0196 (9)	0.0125 (8)	0.0013 (8)	0.0021 (6)	0.0009 (8)
C12	0.0198 (9)	0.0188 (9)	0.0160 (8)	−0.0012 (8)	0.0033 (7)	0.0009 (8)
C13	0.0209 (9)	0.0323 (11)	0.0166 (9)	0.0040 (9)	0.0014 (7)	−0.0025 (8)
C14	0.0205 (9)	0.0156 (8)	0.0150 (8)	−0.0033 (7)	0.0047 (7)	−0.0002 (7)
C15	0.0243 (9)	0.0167 (8)	0.0207 (9)	0.0019 (9)	0.0029 (7)	0.0020 (8)
C16	0.0298 (10)	0.0233 (9)	0.0198 (9)	0.0020 (9)	−0.0026 (8)	0.0030 (8)
C17	0.0379 (12)	0.0260 (11)	0.0140 (9)	−0.0038 (10)	0.0027 (8)	−0.0003 (8)
C18	0.0297 (10)	0.0237 (10)	0.0192 (9)	−0.0001 (9)	0.0067 (8)	−0.0030 (8)
C19	0.0205 (9)	0.0189 (9)	0.0189 (9)	−0.0004 (8)	0.0037 (7)	−0.0004 (7)
C20	0.0156 (8)	0.0154 (8)	0.0130 (8)	−0.0008 (8)	0.0027 (6)	0.0025 (7)
O1W	0.0216 (7)	0.0275 (8)	0.0345 (8)	−0.0031 (6)	0.0074 (6)	−0.0126 (7)

Geometric parameters (Å, º)

O1—C6	1.366 (2)	C5—H51	0.9500
O1—H4	0.86 (3)	C6—C7	1.391 (3)
O2—C9	1.233 (2)	C7—C8	1.394 (3)
O3—C20	1.253 (2)	C7—H71	0.9500
O4—C20	1.258 (2)	C8—H81	0.9500
N1—C1	1.492 (3)	C10—C20	1.540 (2)
N1—H1	0.95 (3)	C10—C11	1.542 (2)
N1—H2	0.99 (3)	C10—H101	1.0000
N1—H3	0.87 (3)	C11—C12	1.509 (3)
N2—C9	1.337 (2)	C11—H111	1.01 (2)
N2—C10	1.462 (2)	C11—H112	0.99 (3)
N2—H5	0.87 (3)	C12—C13	1.371 (3)
N3—C19	1.375 (3)	C12—C14	1.444 (3)
N3—C13	1.380 (3)	C13—H131	0.9500
N3—H6	0.88 (3)	C14—C15	1.401 (3)
C1—C9	1.538 (2)	C14—C19	1.420 (3)
C1—C2	1.541 (3)	C15—C16	1.391 (3)
C1—H11	1.0000	C15—H151	0.9500
C2—C3	1.517 (2)	C16—C17	1.405 (3)
C2—H21	0.9900	C16—H161	0.9500
C2—H22	0.9900	C17—C18	1.383 (3)
C3—C8	1.396 (3)	C17—H171	0.9500
C3—C4	1.398 (3)	C18—C19	1.396 (3)
C4—C5	1.395 (2)	C18—H181	0.9500
C4—H41	0.9500	O1W—H1W	0.850 (18)
C5—C6	1.398 (3)	O1W—H2W	0.857 (18)
C6—O1—H4	111.7 (18)	O2—C9—N2	124.43 (17)
C1—N1—H1	110.7 (18)	O2—C9—C1	120.62 (17)
C1—N1—H2	112.3 (15)	N2—C9—C1	114.95 (15)
H1—N1—H2	103 (2)	N2—C10—C20	111.90 (14)
C1—N1—H3	112 (2)	N2—C10—C11	110.67 (14)
H1—N1—H3	106 (2)	C20—C10—C11	107.91 (15)
H2—N1—H3	112 (3)	N2—C10—H101	108.8
C9—N2—C10	120.51 (15)	C20—C10—H101	108.8
C9—N2—H5	120.8 (16)	C11—C10—H101	108.8
C10—N2—H5	117.9 (16)	C12—C11—C10	116.26 (17)
C19—N3—C13	109.06 (17)	C12—C11—H111	109.5 (14)
C19—N3—H6	128.7 (16)	C10—C11—H111	104.9 (14)
C13—N3—H6	122.3 (17)	C12—C11—H112	111.9 (14)
N1—C1—C9	105.76 (15)	C10—C11—H112	106.9 (15)
N1—C1—C2	110.65 (14)	H111—C11—H112	107 (2)
C9—C1—C2	112.77 (16)	C13—C12—C14	106.15 (17)
N1—C1—H11	109.2	C13—C12—C11	129.14 (18)
C9—C1—H11	109.2	C14—C12—C11	124.62 (17)
C2—C1—H11	109.2	C12—C13—N3	110.28 (18)
C3—C2—C1	114.12 (15)	C12—C13—H131	124.9
C3—C2—H21	108.7	N3—C13—H131	124.9
C1—C2—H21	108.7	C15—C14—C19	118.66 (17)
C3—C2—H22	108.7	C15—C14—C12	134.25 (18)
C1—C2—H22	108.7	C19—C14—C12	107.09 (17)
H21—C2—H22	107.6	C16—C15—C14	118.88 (18)
C8—C3—C4	118.13 (16)	C16—C15—H151	120.6
C8—C3—C2	119.97 (16)	C14—C15—H151	120.6
C4—C3—C2	121.91 (17)	C15—C16—C17	121.27 (19)
C5—C4—C3	120.88 (17)	C15—C16—H161	119.4
C5—C4—H41	119.6	C17—C16—H161	119.4
C3—C4—H41	119.6	C18—C17—C16	121.21 (18)
C4—C5—C6	120.04 (17)	C18—C17—H171	119.4
C4—C5—H51	120.0	C16—C17—H171	119.4
C6—C5—H51	120.0	C17—C18—C19	117.42 (19)
O1—C6—C7	122.73 (17)	C17—C18—H181	121.3
O1—C6—C5	117.45 (17)	C19—C18—H181	121.3
C7—C6—C5	119.80 (16)	N3—C19—C18	130.07 (18)
C6—C7—C8	119.47 (17)	N3—C19—C14	107.39 (16)
C6—C7—H71	120.3	C18—C19—C14	122.54 (18)
C8—C7—H71	120.3	O3—C20—O4	125.55 (17)
C7—C8—C3	121.67 (17)	O3—C20—C10	115.78 (16)
C7—C8—H81	119.2	O4—C20—C10	118.60 (15)
C3—C8—H81	119.2	H1W—O1W—H2W	105 (2)
N1—C1—C9—N2	161.60 (15)	C20—C10—C11—C12	172.80 (16)
C1—C9—N2—C10	177.26 (15)	C10—C11—C12—C14	−125.9 (2)
C9—N2—C10—C20	−67.6 (2)	C14—C12—C13—N3	0.2 (2)
N2—C10—C20—O3	147.54 (16)	C11—C12—C13—N3	176.8 (2)
N1—C1—C2—C3	47.2 (2)	C19—N3—C13—C12	−1.2 (3)
C1—C2—C3—C4	78.8 (2)	C13—C12—C14—C15	−179.8 (2)
N2—C10—C11—C12	−64.5 (2)	C11—C12—C14—C15	3.4 (4)
C10—C11—C12—C13	58.1 (3)	C13—C12—C14—C19	0.8 (2)
C9—C1—C2—C3	−71.0 (2)	C11—C12—C14—C19	−176.03 (18)
C1—C2—C3—C8	−100.8 (2)	C19—C14—C15—C16	0.3 (3)
C8—C3—C4—C5	0.2 (3)	C12—C14—C15—C16	−179.1 (2)
C2—C3—C4—C5	−179.36 (18)	C14—C15—C16—C17	1.1 (3)
C3—C4—C5—C6	0.7 (3)	C15—C16—C17—C18	−1.4 (3)
C4—C5—C6—O1	−179.68 (18)	C16—C17—C18—C19	0.2 (3)
C4—C5—C6—C7	−1.0 (3)	C13—N3—C19—C18	−177.9 (2)
O1—C6—C7—C8	178.95 (19)	C13—N3—C19—C14	1.7 (2)
C5—C6—C7—C8	0.3 (3)	C17—C18—C19—N3	−179.4 (2)
C6—C7—C8—C3	0.6 (3)	C17—C18—C19—C14	1.2 (3)
C4—C3—C8—C7	−0.9 (3)	C15—C14—C19—N3	179.01 (18)
C2—C3—C8—C7	178.70 (17)	C12—C14—C19—N3	−1.5 (2)
C10—N2—C9—O2	−2.5 (3)	C15—C14—C19—C18	−1.4 (3)
N1—C1—C9—O2	−18.6 (2)	C12—C14—C19—C18	178.07 (19)
C2—C1—C9—O2	102.4 (2)	C11—C10—C20—O3	−90.47 (19)
C2—C1—C9—N2	−77.34 (19)	N2—C10—C20—O4	−35.2 (2)
C9—N2—C10—C11	172.00 (16)	C11—C10—C20—O4	86.8 (2)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
N1—H1···O1^i	0.95 (3)	2.16 (3)	2.915 (2)	137 (2)
N1—H2···O1W^ii	0.99 (3)	1.63 (3)	2.611 (2)	170 (2)
N1—H3···C7^iii	0.87 (3)	2.66 (3)	3.298 (3)	131 (2)
O1—H4···O4^i	0.86 (3)	1.86 (3)	2.653 (2)	153 (3)
N2—H5···O3^iv	0.87 (3)	1.96 (3)	2.825 (2)	170 (2)
N3—H6···C14^v	0.88 (3)	2.65 (3)	3.419 (3)	147 (2)
O1W—H1W···O4	0.85 (2)	1.88 (2)	2.725 (2)	177 (3)
O1W—H2W···O3^iv	0.86 (2)	1.81 (2)	2.653 (2)	170 (3)

Symmetry codes: (i) −x+1, y+1/2, −z+1; (ii) x, y+1, z; (iii) −x, y+1/2, −z+1; (iv) x−1, y, z; (v) −x, y+1/2, −z+2.