Cyclo­(alanine-4-hydroxy­proline)

The title compound, 2-hydroxy-6-methyl-1,2,3,5,6,7,8,8a-octa­hydro-7-aza­indolizine-5,8-dione, C₈H₁₂N₂O₂, is bicyclic. The six-membered ring has a boat configuration. The five-membered ring shares one of the prow points and is hinged towards the open part of the boat. Together the rings appear to adopt a slight dish shape. The methyl group is on the open-dish side and the hydroxyl group is trans to it. Hydro­gen bonds in the crystal knit mol­ecules into corrugated layers.

Key indicators

• Single-crystal X-ray study
• T = 293 K
• Mean [sigma](C-C) = 0.004 Å
• R factor = 0.040
• wR factor = 0.096
• Data-to-parameter ratio = 9.2

checkCIF results

No syntax errors found

ADDSYM reports no extra symmetry

General Notes



REFLT_03
         From the CIF: _diffrn_reflns_theta_max           28.01
         From the CIF: _reflns_number_total               1099
         Count of symmetry unique reflns         1100
         Completeness (_total/calc)             99.91%
         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
          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.

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S1. Comment

No comment

S2. Experimental

The title compound was prepared and recrystallized by Zeng (2000) according to the following procedure. L-trans 4-hydroxyproline (with nitrogen protected) and L-alanine methyl ester hydrochloride were reacted in 1:1 chloroform/acetronitrile following the method of Carpino (1986). The reaction was quenched with water and normal work-up of the organic layer afforded the title compound. Crystals were obtained from chloroform solutions.

S3. Refinement

Friedel-pair reflections were merged before final refinement because molybdenum radiation was employed and no atoms heavier than silicon are present in this structure. The absolute structure parameter (Flack parameter and its associated error) was -1.0 with an s.u. of 18.

Computing details

Data collection: Please provide; cell refinement: Please provide; data reduction: Please provide; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEP-3 (Farrugia, 1997).

Figures

Fig. 1. The structure of (I) showing 50% displacement ellipsoids.

2-hydroxy-6-methyl-1,2,3,5,6,7,8,8a-octahydro-7-azaindolizine-5,8-dione

Crystal data

C8H12N2O3	F(000) = 196
Mr = 184.20	Dx = 1.420 Mg m^−3
Monoclinic, P21	Mo Kα radiation, λ = 0.71070 Å
a = 8.626 (2) Å	Cell parameters from 16 reflections
b = 9.924 (3) Å	θ = 11–13°
c = 5.179 (1) Å	µ = 0.11 mm^−1
β = 103.719 (9)°	T = 293 K
V = 430.70 (18) Å^3	Prism, colorless
Z = 2	0.45 × 0.30 × 0.20 mm

Data collection

MAKER? four-circle diffractometer	Rint = 0.035
Radiation source: fine-focus sealed tube	θmax = 28.0°, θmin = 2.4°
None monochromator	h = −9→11
θ/2θ scans	k = −10→13
2100 measured reflections	l = −6→4
1099 independent reflections	3 standard reflections every 150 reflections
835 reflections with I > 2σ(I)	intensity decay: <1%

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)] = 0.040	H-atom parameters constrained
wR(F^2) = 0.096	w = 1/[σ^2(Fo^2) + (0.0264P)^2] where P = (Fo^2 + 2Fc^2)/3
S = 0.99	(Δ/σ)max < 0.001
1099 reflections	Δρmax = 0.20 e Å^−3
120 parameters	Δρmin = −0.18 e Å^−3
1 restraint	Extinction correction: SHELXL97, Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.074 (13)

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. Refinement of F² against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F², conventional R-factors R are based on F, with F set to zero for negative F². The threshold expression of F² > σ(F²) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F² are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger.

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

	x	y	z	Uiso*/Ueq
C1	0.2467 (3)	0.6102 (3)	0.3226 (5)	0.0347 (6)
C2	−0.0077 (3)	0.4887 (3)	0.2753 (5)	0.0342 (6)
H2	−0.0731	0.5261	0.1098	0.041*
C3	0.0726 (3)	0.3612 (3)	0.2082 (5)	0.0325 (6)
C4	0.2801 (3)	0.5138 (3)	0.1155 (5)	0.0325 (6)
H4	0.2393	0.5525	−0.0617	0.039*
C5	0.4557 (4)	0.4786 (3)	0.1508 (6)	0.0408 (7)
H5A	0.5094	0.4739	0.3377	0.049*
H5B	0.5092	0.5449	0.0648	0.049*
C6	0.4536 (3)	0.3413 (3)	0.0187 (6)	0.0390 (7)
H6	0.5517	0.2911	0.0942	0.047*
C7	0.3088 (4)	0.2714 (3)	0.0811 (7)	0.0444 (7)
H7A	0.2542	0.2162	−0.0674	0.053*
H7B	0.3406	0.2149	0.2375	0.053*
C8	−0.1152 (4)	0.4593 (3)	0.4595 (8)	0.0524 (8)
H8A	−0.1638	0.5415	0.4984	0.079*
H8B	−0.0534	0.4209	0.6216	0.079*
H8C	−0.1966	0.3969	0.3758	0.079*
N1	0.1110 (3)	0.5890 (2)	0.3947 (4)	0.0350 (5)
H1	0.0918	0.6379	0.5206	0.042*
N2	0.2062 (3)	0.3816 (2)	0.1281 (4)	0.0342 (5)
O1	0.3407 (3)	0.7007 (2)	0.4120 (4)	0.0514 (6)
O2	0.0168 (2)	0.24882 (19)	0.2236 (4)	0.0466 (6)
O3	0.4307 (3)	0.3558 (3)	−0.2594 (4)	0.0625 (7)
H3	0.4828	0.2984	−0.3154	0.075*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
C1	0.0388 (15)	0.0284 (13)	0.0396 (15)	0.0003 (11)	0.0148 (11)	0.0010 (11)
C2	0.0323 (14)	0.0318 (14)	0.0383 (14)	0.0023 (11)	0.0076 (11)	−0.0003 (11)
C3	0.0348 (14)	0.0324 (14)	0.0303 (13)	−0.0034 (11)	0.0076 (10)	−0.0002 (11)
C4	0.0400 (14)	0.0284 (12)	0.0324 (13)	0.0000 (11)	0.0149 (11)	0.0017 (11)
C5	0.0385 (15)	0.0388 (15)	0.0511 (16)	−0.0005 (12)	0.0225 (13)	0.0014 (13)
C6	0.0381 (15)	0.0413 (16)	0.0395 (15)	0.0094 (12)	0.0130 (12)	0.0044 (12)
C7	0.0502 (16)	0.0330 (15)	0.0531 (19)	0.0011 (13)	0.0188 (14)	−0.0092 (13)
C8	0.0410 (16)	0.0476 (17)	0.077 (2)	−0.0074 (14)	0.0311 (16)	−0.0152 (17)
N1	0.0391 (13)	0.0283 (12)	0.0417 (13)	−0.0034 (10)	0.0179 (10)	−0.0077 (9)
N2	0.0375 (12)	0.0265 (11)	0.0412 (13)	−0.0003 (10)	0.0142 (9)	−0.0061 (10)
O1	0.0528 (13)	0.0426 (12)	0.0674 (16)	−0.0181 (10)	0.0313 (11)	−0.0189 (11)
O2	0.0511 (12)	0.0339 (11)	0.0607 (15)	−0.0104 (9)	0.0249 (11)	−0.0040 (9)
O3	0.0801 (17)	0.0728 (17)	0.0421 (12)	0.0356 (13)	0.0295 (11)	0.0071 (11)

Geometric parameters (Å, º)

C1—O1	1.225 (3)	C5—H5A	0.9700
C1—N1	1.327 (3)	C5—H5B	0.9700
C1—C4	1.515 (3)	C6—O3	1.414 (4)
C2—N1	1.456 (3)	C6—C7	1.529 (4)
C2—C8	1.508 (4)	C6—H6	0.9800
C2—C3	1.522 (4)	C7—N2	1.463 (4)
C2—H2	0.9800	C7—H7A	0.9700
C3—O2	1.225 (3)	C7—H7B	0.9700
C3—N2	1.330 (3)	C8—H8A	0.9600
C4—N2	1.467 (3)	C8—H8B	0.9600
C4—C5	1.523 (4)	C8—H8C	0.9600
C4—H4	0.9800	N1—H1	0.8600
C5—C6	1.523 (4)	O3—H3	0.8200
O1—C1—N1	124.0 (2)	O3—C6—C7	109.7 (2)
O1—C1—C4	120.7 (3)	C5—C6—C7	103.5 (2)
N1—C1—C4	115.3 (2)	O3—C6—H6	110.9
N1—C2—C8	109.8 (2)	C5—C6—H6	110.9
N1—C2—C3	110.7 (2)	C7—C6—H6	110.9
C8—C2—C3	111.4 (2)	N2—C7—C6	104.7 (2)
N1—C2—H2	108.3	N2—C7—H7A	110.8
C8—C2—H2	108.3	C6—C7—H7A	110.8
C3—C2—H2	108.3	N2—C7—H7B	110.8
O2—C3—N2	122.9 (3)	C6—C7—H7B	110.8
O2—C3—C2	122.3 (2)	H7A—C7—H7B	108.9
N2—C3—C2	114.8 (2)	C2—C8—H8A	109.5
N2—C4—C1	112.1 (2)	C2—C8—H8B	109.5
N2—C4—C5	102.7 (2)	H8A—C8—H8B	109.5
C1—C4—C5	114.2 (2)	C2—C8—H8C	109.5
N2—C4—H4	109.2	H8A—C8—H8C	109.5
C1—C4—H4	109.2	H8B—C8—H8C	109.5
C5—C4—H4	109.2	C1—N1—C2	124.5 (2)
C4—C5—C6	104.2 (2)	C1—N1—H1	117.7
C4—C5—H5A	110.9	C2—N1—H1	117.7
C6—C5—H5A	110.9	C3—N2—C4	124.6 (2)
C4—C5—H5B	110.9	C3—N2—C7	122.7 (2)
C6—C5—H5B	110.9	C4—N2—C7	112.0 (2)
H5A—C5—H5B	108.9	C6—O3—H3	109.5
O3—C6—C5	110.5 (2)
N1—C2—C3—O2	145.8 (3)	O1—C1—N1—C2	174.9 (3)
C8—C2—C3—O2	23.3 (4)	C4—C1—N1—C2	−4.7 (4)
N1—C2—C3—N2	−35.2 (3)	C8—C2—N1—C1	160.8 (2)
C8—C2—C3—N2	−157.7 (2)	C3—C2—N1—C1	37.4 (3)
O1—C1—C4—N2	151.9 (3)	O2—C3—N2—C4	−177.8 (3)
N1—C1—C4—N2	−28.5 (3)	C2—C3—N2—C4	3.2 (4)
O1—C1—C4—C5	35.6 (4)	O2—C3—N2—C7	−7.4 (4)
N1—C1—C4—C5	−144.7 (2)	C2—C3—N2—C7	173.6 (2)
N2—C4—C5—C6	33.0 (3)	C1—C4—N2—C3	29.7 (4)
C1—C4—C5—C6	154.5 (2)	C5—C4—N2—C3	152.7 (2)
C4—C5—C6—O3	82.0 (3)	C1—C4—N2—C7	−141.6 (3)
C4—C5—C6—C7	−35.5 (3)	C5—C4—N2—C7	−18.5 (3)
O3—C6—C7—N2	−94.0 (3)	C6—C7—N2—C3	−174.9 (2)
C5—C6—C7—N2	23.9 (3)	C6—C7—N2—C4	−3.4 (3)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
N1—H1···O2^i	0.86	2.10	2.945 (3)	165
O3—H3···O1^ii	0.82	1.97	2.761 (3)	163

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