Cyclo­(L-isoleucyl-L-isoleuc­yl)

The title compound [systematic name: (3S,6S)-3,6-bis­(S-sec-but­yl)-2,5-piperazine-2,5-dione], C₁₂H₂₂N₂O₂, was crystallized from a solution of the corresponding linear peptide L-iso­leucyl-L-isoleucine. In the crystal structure, mol­ecules form traditional N—H...O hydrogen-bonded tapes along the a axis [a = 6.242 (9) Å].

Key indicators

• Single-crystal X-ray study
• T = 105 K
• Mean [sigma](C-C) = 0.004 Å
• R factor = 0.036
• wR factor = 0.106
• Data-to-parameter ratio = 11.1

checkCIF/PLATON results

No syntax errors found



Alert level A
PLAT063_ALERT_3_A Crystal Probably too Large for Beam Size .......       1.30 mm

Author Response: This is no problem for a light atom structure, see Gorbitz, Acta Cryst. B55 (1999) 1090-98.

Alert level B
CRYSS02_ALERT_3_B  The value of _exptl_crystal_size_max is > 1.0
   Maximum crystal size given =   1.300
PLAT220_ALERT_2_B Large Non-Solvent    C     Ueq(max)/Ueq(min) ...       3.99 Ratio
PLAT222_ALERT_3_B Large Non-Solvent    H     Ueq(max)/Ueq(min) ...       4.81 Ratio

Alert level C
ABSTM02_ALERT_3_C  The ratio of expected to reported Tmax/Tmin(RR') is < 0.90
            Tmin and Tmax reported:      0.766     0.994
            Tmin(prime) and Tmax expected:      0.905     0.994
            RR(prime) =      0.847
            Please check that your absorption correction is appropriate.
PLAT029_ALERT_3_C _diffrn_measured_fraction_theta_full Low .......       0.98
PLAT061_ALERT_3_C Tmax/Tmin Range Test RR' too Large .............       0.85
PLAT480_ALERT_4_C Long H...A H-Bond Reported H71    ..  O1      ..       2.61 Ang.

Alert level G
REFLT03_ALERT_1_G ALERT: Expected hkl max differ from CIF values
           From the CIF: _diffrn_reflns_theta_max           28.18
           From the CIF: _reflns_number_total               1739
           From the CIF: _diffrn_reflns_limit_ max hkl    8.   14.   21.
           From the CIF: _diffrn_reflns_limit_ min hkl   -7.   -9.  -24.
           TEST1: Expected hkl limits for theta max
           Calculated maximum hkl    8.   14.   26.
           Calculated minimum hkl   -8.  -14.  -26.
REFLT03_ALERT_4_G Please check that the estimate of the number of Friedel pairs is
            correct. If it is not, please give the correct count in the
            _publ_section_exptl_refinement section of the submitted CIF.
           From the CIF: _diffrn_reflns_theta_max           28.18
           From the CIF: _reflns_number_total               1739
           Count of symmetry unique reflns         1906
           Completeness (_total/calc)             91.24%
           TEST3: Check Friedels for noncentro structure
           Estimate of Friedel pairs measured         0
           Fraction of Friedel pairs measured     0.000
           Are heavy atom types Z>Si present         no

   1 ALERT level A = In general: serious problem
   3 ALERT level B = Potentially serious problem
   4 ALERT level C = Check and explain
   2 ALERT level G = General alerts; check

   1 ALERT type 1 CIF construction/syntax error, inconsistent or missing data
   1 ALERT type 2 Indicator that the structure model may be wrong or deficient
   6 ALERT type 3 Indicator that the structure quality may be low
   2 ALERT type 4 Improvement, methodology, query or suggestion

---

Computing details

Data collection: SMART (Bruker, 1998); cell refinement: SAINT-Plus (Bruker, 2001); data reduction: SAINT; program(s) used to solve structure: SHELXTL (Bruker, 2000); program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL.

(3S,6S)-3,6-bis(S-sec-butyl)-2,5-piperazine-2,5-dione

Crystal data

C12H22N2O2	F(000) = 496
Mr = 226.32	Dx = 1.125 Mg m^−3
Orthorhombic, P212121	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: P 2ac 2ab	Cell parameters from 4248 reflections
a = 6.242 (9) Å	θ = 2.1–28.2°
b = 10.814 (15) Å	µ = 0.08 mm^−1
c = 19.79 (3) Å	T = 105 K
V = 1336 (3) Å^3	Needle, colourless
Z = 4	1.30 × 0.10 × 0.08 mm

Data collection

Siemens SMART CCD diffractometer	1739 independent reflections
Radiation source: fine-focus sealed tube	1557 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.040
Detector resolution: 8.3 pixels mm^-1	θmax = 28.2°, θmin = 2.1°
Sets of exposures each taken over 0.3° ω rotation scans	h = −7→8
Absorption correction: multi-scan (SADABS; Sheldrick, 1996)	k = −9→14
Tmin = 0.766, Tmax = 0.994	l = −24→21
7470 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) = 0.106	H atoms treated by a mixture of independent and constrained refinement
S = 1.09	w = 1/[σ^2(Fo^2) + (0.0514P)^2 + 0.2942P] where P = (Fo^2 + 2Fc^2)/3
1739 reflections	(Δ/σ)max = 0.006
156 parameters	Δρmax = 0.30 e Å^−3
0 restraints	Δρmin = −0.19 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	0.2228 (2)	0.63275 (14)	0.38440 (7)	0.0252 (3)
O2	0.9431 (2)	0.59081 (13)	0.53186 (7)	0.0242 (3)
N1	0.7847 (2)	0.62047 (15)	0.43045 (8)	0.0187 (3)
H1	0.915 (4)	0.626 (2)	0.4124 (11)	0.022*
N2	0.3810 (2)	0.59519 (16)	0.48512 (8)	0.0193 (3)
H2	0.245 (4)	0.590 (2)	0.5013 (11)	0.023*
C1	0.6032 (3)	0.64716 (16)	0.38577 (9)	0.0178 (4)
H11	0.6096	0.7372	0.3744	0.021*
C2	0.6208 (3)	0.57451 (19)	0.31863 (10)	0.0232 (4)
H21	0.4883	0.5924	0.2920	0.028*
C3	0.6267 (4)	0.4342 (2)	0.33129 (12)	0.0386 (6)
H32	0.7563	0.4143	0.3580	0.046*
H31	0.5004	0.4110	0.3587	0.046*
C4	0.6278 (6)	0.3557 (3)	0.26683 (16)	0.0676 (10)
H43	0.7643	0.3670	0.2432	0.101*
H42	0.5099	0.3817	0.2374	0.101*
H41	0.6100	0.2684	0.2787	0.101*
C5	0.8121 (3)	0.6206 (3)	0.27678 (11)	0.0401 (6)
H53	0.9459	0.5943	0.2983	0.060*
H52	0.8083	0.7111	0.2742	0.060*
H51	0.8042	0.5858	0.2311	0.060*
C6	0.3868 (3)	0.62341 (17)	0.41899 (9)	0.0183 (4)
C7	0.5611 (3)	0.59603 (16)	0.53249 (9)	0.0182 (4)
H71	0.5470	0.6722	0.5608	0.022*
C8	0.5530 (3)	0.48314 (17)	0.58103 (9)	0.0209 (4)
H81	0.6841	0.4870	0.6100	0.025*
C9	0.5599 (4)	0.35908 (18)	0.54281 (11)	0.0313 (5)
H92	0.4175	0.3433	0.5225	0.038*
H91	0.6650	0.3654	0.5055	0.038*
C10	0.6205 (5)	0.2492 (2)	0.58803 (13)	0.0463 (7)
H103	0.5267	0.2476	0.6277	0.069*
H102	0.7698	0.2577	0.6026	0.069*
H101	0.6038	0.1720	0.5626	0.069*
C11	0.3586 (3)	0.4927 (2)	0.62814 (11)	0.0313 (5)
H113	0.2266	0.4880	0.6014	0.047*
H112	0.3631	0.5717	0.6524	0.047*
H111	0.3617	0.4245	0.6607	0.047*
C12	0.7784 (3)	0.60210 (17)	0.49755 (9)	0.0169 (4)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
O1	0.0143 (6)	0.0410 (8)	0.0201 (7)	0.0013 (6)	−0.0015 (5)	0.0035 (6)
O2	0.0139 (6)	0.0393 (8)	0.0195 (7)	0.0003 (6)	−0.0004 (5)	0.0022 (6)
N1	0.0123 (7)	0.0268 (8)	0.0171 (7)	−0.0011 (6)	0.0019 (6)	−0.0004 (6)
N2	0.0108 (7)	0.0291 (8)	0.0180 (8)	0.0001 (6)	0.0018 (6)	0.0032 (6)
C1	0.0147 (8)	0.0204 (8)	0.0182 (8)	−0.0004 (7)	−0.0003 (7)	0.0017 (7)
C2	0.0171 (9)	0.0338 (10)	0.0188 (9)	0.0018 (8)	−0.0015 (8)	−0.0034 (8)
C3	0.0454 (14)	0.0306 (11)	0.0398 (13)	0.0081 (10)	−0.0105 (12)	−0.0126 (10)
C4	0.082 (2)	0.0570 (17)	0.0636 (19)	0.0110 (17)	−0.0232 (19)	−0.0375 (15)
C5	0.0222 (10)	0.0745 (18)	0.0236 (11)	−0.0044 (11)	0.0042 (9)	−0.0079 (12)
C6	0.0156 (8)	0.0215 (8)	0.0179 (8)	0.0014 (7)	0.0002 (7)	0.0010 (7)
C7	0.0130 (8)	0.0227 (9)	0.0188 (9)	0.0001 (7)	0.0016 (7)	−0.0010 (7)
C8	0.0167 (8)	0.0271 (9)	0.0189 (8)	0.0007 (7)	−0.0006 (7)	0.0044 (7)
C9	0.0357 (11)	0.0267 (10)	0.0314 (11)	−0.0008 (9)	−0.0029 (10)	0.0023 (8)
C10	0.0582 (16)	0.0305 (12)	0.0503 (15)	0.0069 (11)	0.0150 (14)	0.0120 (11)
C11	0.0196 (9)	0.0468 (13)	0.0275 (11)	0.0046 (9)	0.0049 (8)	0.0135 (9)
C12	0.0126 (8)	0.0205 (9)	0.0177 (9)	−0.0001 (7)	−0.0001 (7)	−0.0015 (7)

Geometric parameters (Å, º)

O1—C6	1.236 (3)	C4—H41	0.9800
O2—C12	1.238 (3)	C5—H53	0.9800
N1—C12	1.343 (3)	C5—H52	0.9800
N1—C1	1.466 (3)	C5—H51	0.9800
N1—H1	0.89 (2)	C7—C12	1.524 (3)
N2—C6	1.345 (3)	C7—C8	1.554 (3)
N2—C7	1.464 (3)	C7—H71	1.0000
N2—H2	0.91 (2)	C8—C11	1.534 (3)
C1—C6	1.524 (3)	C8—C9	1.541 (3)
C1—C2	1.548 (3)	C8—H81	1.0000
C1—H11	1.0000	C9—C10	1.535 (3)
C2—C5	1.536 (3)	C9—H92	0.9900
C2—C3	1.539 (4)	C9—H91	0.9900
C2—H21	1.0000	C10—H103	0.9800
C3—C4	1.532 (4)	C10—H102	0.9800
C3—H32	0.9900	C10—H101	0.9800
C3—H31	0.9900	C11—H113	0.9800
C4—H43	0.9800	C11—H112	0.9800
C4—H42	0.9800	C11—H111	0.9800
C12—N1—C1	127.06 (16)	O1—C6—N2	122.36 (17)
C12—N1—H1	115.7 (14)	O1—C6—C1	118.80 (18)
C1—N1—H1	116.8 (14)	N2—C6—C1	118.84 (16)
C6—N2—C7	126.96 (16)	N2—C7—C12	113.16 (17)
C6—N2—H2	112.5 (14)	N2—C7—C8	111.49 (16)
C7—N2—H2	119.4 (14)	C12—C7—C8	110.05 (14)
N1—C1—C6	113.06 (17)	N2—C7—H71	107.3
N1—C1—C2	111.30 (16)	C12—C7—H71	107.3
C6—C1—C2	110.35 (15)	C8—C7—H71	107.3
N1—C1—H11	107.3	C11—C8—C9	112.27 (18)
C6—C1—H11	107.3	C11—C8—C7	110.38 (16)
C2—C1—H11	107.3	C9—C8—C7	112.30 (19)
C5—C2—C3	112.9 (2)	C11—C8—H81	107.2
C5—C2—C1	110.70 (18)	C9—C8—H81	107.2
C3—C2—C1	111.25 (18)	C7—C8—H81	107.2
C5—C2—H21	107.2	C10—C9—C8	113.2 (2)
C3—C2—H21	107.2	C10—C9—H92	108.9
C1—C2—H21	107.2	C8—C9—H92	108.9
C4—C3—C2	114.2 (2)	C10—C9—H91	108.9
C4—C3—H32	108.7	C8—C9—H91	108.9
C2—C3—H32	108.7	H92—C9—H91	107.7
C4—C3—H31	108.7	C9—C10—H103	109.5
C2—C3—H31	108.7	C9—C10—H102	109.5
H32—C3—H31	107.6	H103—C10—H102	109.5
C3—C4—H43	109.5	C9—C10—H101	109.5
C3—C4—H42	109.5	H103—C10—H101	109.5
H43—C4—H42	109.5	H102—C10—H101	109.5
C3—C4—H41	109.5	C8—C11—H113	109.5
H43—C4—H41	109.5	C8—C11—H112	109.5
H42—C4—H41	109.5	H113—C11—H112	109.5
C2—C5—H53	109.5	C8—C11—H111	109.5
C2—C5—H52	109.5	H113—C11—H111	109.5
H53—C5—H52	109.5	H112—C11—H111	109.5
C2—C5—H51	109.5	O2—C12—N1	122.17 (17)
H53—C5—H51	109.5	O2—C12—C7	119.08 (18)
H52—C5—H51	109.5	N1—C12—C7	118.75 (16)
C12—N1—C1—C6	−13.7 (2)	C6—C1—C2—C3	−67.0 (2)
N1—C1—C6—N2	7.1 (2)	C5—C2—C3—C4	−59.0 (3)
C1—C6—N2—C7	6.6 (3)	C7—N2—C6—O1	−172.20 (17)
N1—C1—C2—C3	59.4 (2)	N1—C1—C6—O1	−174.02 (17)
N1—C1—C2—C5	−67.0 (2)	C2—C1—C6—O1	−48.7 (2)
C1—C2—C3—C4	175.8 (2)	C2—C1—C6—N2	132.51 (19)
C6—N2—C7—C12	−14.3 (2)	C6—N2—C7—C8	−138.94 (19)
N2—C7—C12—N1	7.7 (2)	C12—C7—C8—C11	166.93 (15)
C7—C12—N1—C1	6.0 (3)	C12—C7—C8—C9	−67.0 (2)
N2—C7—C8—C9	59.4 (2)	C11—C8—C9—C10	−72.4 (3)
N2—C7—C8—C11	−66.7 (2)	C1—N1—C12—O2	−173.51 (17)
C7—C8—C9—C10	162.49 (19)	N2—C7—C12—O2	−172.80 (18)
C12—N1—C1—C2	−138.5 (2)	C8—C7—C12—O2	−47.3 (2)
C6—C1—C2—C5	166.59 (16)	C8—C7—C12—N1	133.14 (18)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
N1—H1···O1^i	0.89 (2)	2.00 (2)	2.885 (4)	172 (2)
N2—H2···O2^ii	0.91 (2)	1.98 (2)	2.886 (4)	175 (2)
C5—H53···O1^i	0.98	2.46	3.336 (4)	148
C7—H71···O1^iii	1.00	2.61	3.511 (4)	149
C11—H113···O2^ii	0.98	2.50	3.389 (4)	150

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