O-Benzyl-N-tert-butoxy­carbonyl-L-threonyl-L-proline trichloro­ethyl ester [Boc-L-Thr(Bzl)-L-Pro-OTce]

The title peptide compound, C₂₃H₃₁Cl₃N₂O₆, is a synthetic inter­mediate as a plasmodium falciparum blood-stage antigen. There is an intra­molecular N—H...O hydrogen bond between the urethane and benzyl ether groups. The relatively low melting point is attributed to the lack of an inter­molecular hydrogen-bond network.

Key indicators

• Single-crystal X-ray study
• T = 173 K
• Mean [sigma](C-C) = 0.009 Å
• R factor = 0.063
• wR factor = 0.145
• Data-to-parameter ratio = 13.7

checkCIF/PLATON results

No syntax errors found



Alert level C
PLAT026_ALERT_3_C Ratio Observed / Unique Reflections too Low ....         46 Perc.

Author Response: Diffractions from the crystal of (I) were too weak to collect enough numbers, even we have used many techniques to increase the number data available (low temperature, Cu-K(alpha) radiationan, area detector).

PLAT331_ALERT_2_C Small Average Phenyl C-C Dist.   C206   -C211          1.37 Ang.

Author Response: It is due to the difference of thermal mobility. The atoms located at chain-ends (Boc- and -OEt) and amino-acid side chains often show higer U(eq) compared with the atoms located inside of the molecule.

PLAT340_ALERT_3_C Low Bond Precision on C-C bonds (x 1000) Ang ...          9

Author Response: This is probably due to the higher thermal mobility of the Boc- and Thr(Bzl) compared with the atoms located in the Pro (except C301-C302) and -OTce.

Alert level G
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           68.24
           From the CIF: _reflns_number_total               4647
           Count of symmetry unique reflns         2671
           Completeness (_total/calc)            173.98%
           TEST3: Check Friedels for noncentro structure
           Estimate of Friedel pairs measured      1976
           Fraction of Friedel pairs measured     0.740
           Are heavy atom types Z>Si present        yes

Author Response: We have checked the number of Friedel pairs is correct.

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

   0 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
   2 ALERT type 3 Indicator that the structure quality may be low
   1 ALERT type 4 Improvement, methodology, query or suggestion

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Computing details

Data collection: RAPID-AUTO (Rigaku/MSC, 2003); cell refinement: RAPID-AUTO; data reduction: CrystalStructure (Rigaku/MSC, 2003); program(s) used to solve structure: SIR2002 (Burla et al., 2003); program(s) used to refine structure: CRYSTALS (Betteridge et al., 2003); molecular graphics: ORTEP (Johnson, 1965); software used to prepare material for publication: CrystalStructure.

N-tert-Butoxycarbonyl-O-benzyl-L-threonyl-L-proline trichloroethyl ester

Crystal data

C23H31Cl3N2O6	Dx = 1.391 Mg m^−3
Mr = 537.87	Melting point = 371–372 K
Orthorhombic, P212121	Cu Kα radiation, λ = 1.5418 Å
Hall symbol: P 2ac 2ab	Cell parameters from 21410 reflections
a = 11.311 (9) Å	θ = 3.9–67.2°
b = 11.693 (7) Å	µ = 3.58 mm^−1
c = 19.417 (12) Å	T = 173 K
V = 2568 (3) Å^3	Platelet, colorless
Z = 4	0.05 × 0.02 × 0.01 mm
F(000) = 1128.00

Data collection

Rigaku R-AXIS RAPID diffractometer	Rint = 0.071
Detector resolution: 10.00 pixels mm^-1	θmax = 68.2°
ω scans	h = −13→13
20848 measured reflections	k = −14→14
4647 independent reflections	l = −23→23
2140 reflections with F^2 > 2σ(F^2)

Refinement

Refinement on F^2	w = 4Fo^2/[0.0008Fo^2 + σ(Fo^2)]
R[F^2 > 2σ(F^2)] = 0.063	(Δ/σ)max < 0.001
wR(F^2) = 0.145	Δρmax = 0.74 e Å^−3
S = 0.97	Δρmin = −1.01 e Å^−3
4647 reflections	Absolute structure: Flack (1983), 1983 Friedel pairs
339 parameters	Absolute structure parameter: 0.16 (2)
H-atom parameters constrained

Special details

Refinement. Refinement using all reflections. The weighted R-factor (wR) and goodness of fit (S) are based on F². R-factor (gt) are based on F. The threshold expression of F² > 2.0 σ(F²) is used only for calculating R-factor (gt).

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

	x	y	z	Uiso*/Ueq
Cl41	0.64804 (14)	0.31124 (14)	−0.07075 (10)	0.0629 (5)
Cl42	0.56749 (17)	0.34932 (16)	−0.20790 (9)	0.0690 (6)
Cl43	0.42593 (16)	0.21642 (13)	−0.11478 (10)	0.0643 (5)
O101	0.5397 (3)	0.9723 (3)	0.1340 (2)	0.0496 (13)
O102	0.6925 (3)	0.9815 (3)	0.0561 (2)	0.0558 (14)
O201	0.5083 (4)	0.7760 (3)	−0.0206 (2)	0.0535 (14)
O202	0.5752 (3)	0.5957 (3)	0.0978 (2)	0.0499 (13)
O301	0.4123 (4)	0.6333 (3)	−0.1700 (2)	0.0658 (16)
O401	0.5328 (3)	0.5349 (3)	−0.0986 (2)	0.0513 (14)
N201	0.6263 (4)	0.8126 (4)	0.0997 (2)	0.0440 (16)
N301	0.6692 (4)	0.7160 (4)	−0.0765 (2)	0.0447 (16)
C101	0.5159 (6)	1.0953 (5)	0.1346 (3)	0.051 (2)
C102	0.6235 (5)	1.1629 (5)	0.1559 (3)	0.062 (2)
C103	0.4142 (5)	1.1059 (5)	0.1859 (3)	0.066 (2)
C104	0.4747 (5)	1.1322 (5)	0.0647 (3)	0.059 (2)
C105	0.6247 (6)	0.9287 (5)	0.0933 (3)	0.054 (2)
C201	0.6852 (5)	0.7437 (5)	0.0481 (3)	0.044 (2)
C202	0.6155 (5)	0.7501 (5)	−0.0189 (3)	0.042 (2)
C203	0.6927 (5)	0.6215 (4)	0.0739 (3)	0.048 (2)
C204	0.7850 (5)	0.6064 (5)	0.1286 (3)	0.064 (2)
C205	0.5478 (5)	0.4782 (4)	0.1035 (3)	0.056 (2)
C206	0.4235 (6)	0.4666 (5)	0.1282 (3)	0.048 (2)
C207	0.3990 (6)	0.4303 (5)	0.1932 (3)	0.057 (2)
C208	0.2848 (6)	0.4217 (5)	0.2168 (3)	0.052 (2)
C209	0.1917 (5)	0.4530 (5)	0.1759 (3)	0.050 (2)
C210	0.2140 (6)	0.4905 (5)	0.1097 (3)	0.054 (2)
C211	0.3299 (6)	0.4951 (5)	0.0879 (3)	0.058 (2)
C301	0.6021 (5)	0.7115 (5)	−0.1405 (3)	0.048 (2)
C302	0.5033 (6)	0.6275 (5)	−0.1387 (3)	0.054 (2)
C303	0.6941 (5)	0.6794 (5)	−0.1940 (3)	0.054 (2)
C304	0.8137 (5)	0.7166 (5)	−0.1627 (3)	0.051 (2)
C305	0.7965 (5)	0.6919 (5)	−0.0859 (2)	0.053 (2)
C401	0.4527 (6)	0.4396 (4)	−0.0985 (3)	0.060 (2)
C402	0.5208 (5)	0.3351 (5)	−0.1216 (3)	0.053 (2)
H1	0.5900	0.7758	0.1378	0.053*
H2	0.1132	0.4508	0.1933	0.060*
H3	0.3462	0.5209	0.0425	0.069*
H4	0.7105	0.5730	0.0361	0.057*
H5	0.5710	0.7851	−0.1507	0.058*
H6	0.3402	1.0966	0.1634	0.080*
H7	0.4176	1.1794	0.2066	0.080*
H8	0.4226	1.0489	0.2205	0.080*
H9	0.6199	1.1720	0.2045	0.075*
H10	0.6247	1.2360	0.1346	0.075*
H11	0.6932	1.1221	0.1440	0.075*
H12	0.7626	0.7730	0.0410	0.053*
H13	0.5563	0.4413	0.0602	0.067*
H14	0.6000	0.4441	0.1359	0.067*
H15	0.8263	0.7960	−0.1700	0.061*
H16	0.8780	0.6746	−0.1814	0.061*
H17	0.8438	0.7401	−0.0577	0.064*
H18	0.8143	0.6142	−0.0761	0.064*
H19	0.4225	0.4275	−0.0534	0.072*
H20	0.3890	0.4537	−0.1293	0.072*
H21	0.2699	0.3921	0.2616	0.063*
H22	0.5410	1.1551	0.0381	0.071*
H23	0.4209	1.1943	0.0686	0.071*
H24	0.4365	1.0696	0.0429	0.071*
H25	0.7956	0.6782	0.1507	0.077*
H26	0.8578	0.5823	0.1091	0.077*
H27	0.7591	0.5515	0.1614	0.077*
H28	0.6931	0.5988	−0.2000	0.064*
H29	0.6799	0.7158	−0.2369	0.064*
H30	0.1508	0.5105	0.0799	0.065*
H31	0.4633	0.4094	0.2221	0.069*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Cl41	0.0607 (11)	0.0582 (11)	0.0698 (12)	0.0017 (9)	−0.0083 (10)	0.0002 (10)
Cl42	0.0809 (13)	0.0710 (12)	0.0551 (11)	−0.0037 (11)	0.0055 (10)	−0.0088 (9)
Cl43	0.0660 (11)	0.0517 (10)	0.0752 (12)	−0.0060 (9)	−0.0046 (10)	−0.0041 (9)
O101	0.060 (3)	0.039 (2)	0.050 (2)	−0.000 (2)	0.010 (2)	0.000 (2)
O102	0.064 (3)	0.048 (2)	0.055 (3)	−0.004 (2)	0.008 (2)	0.001 (2)
O201	0.055 (2)	0.060 (2)	0.045 (2)	0.000 (2)	0.001 (2)	0.004 (2)
O202	0.048 (2)	0.038 (2)	0.063 (3)	−0.002 (2)	0.009 (2)	−0.000 (2)
O301	0.055 (3)	0.064 (3)	0.078 (3)	−0.002 (2)	−0.021 (2)	0.005 (2)
O401	0.044 (2)	0.050 (2)	0.060 (3)	−0.003 (2)	−0.002 (2)	−0.004 (2)
N201	0.066 (3)	0.043 (3)	0.024 (2)	−0.001 (2)	0.007 (2)	0.001 (2)
N301	0.044 (3)	0.052 (3)	0.039 (3)	0.000 (2)	−0.007 (2)	0.002 (2)
C101	0.061 (4)	0.036 (4)	0.055 (4)	−0.002 (3)	0.008 (3)	0.002 (3)
C102	0.067 (5)	0.045 (4)	0.075 (5)	0.006 (3)	−0.016 (4)	0.001 (4)
C103	0.064 (5)	0.046 (4)	0.089 (5)	0.009 (3)	0.012 (4)	0.001 (3)
C104	0.067 (5)	0.048 (4)	0.063 (4)	0.001 (3)	0.002 (4)	0.003 (3)
C105	0.065 (5)	0.046 (4)	0.052 (5)	−0.013 (3)	−0.003 (4)	−0.002 (3)
C201	0.043 (4)	0.048 (4)	0.041 (4)	−0.004 (3)	−0.001 (3)	0.000 (3)
C202	0.048 (4)	0.045 (4)	0.032 (4)	−0.007 (3)	0.003 (3)	0.003 (3)
C203	0.058 (4)	0.038 (3)	0.048 (4)	−0.008 (3)	−0.003 (3)	−0.004 (3)
C204	0.058 (4)	0.065 (5)	0.070 (5)	−0.003 (3)	0.000 (4)	0.009 (4)
C205	0.062 (4)	0.034 (3)	0.072 (5)	0.001 (3)	0.003 (4)	−0.003 (3)
C206	0.043 (4)	0.046 (4)	0.054 (4)	−0.006 (3)	−0.005 (4)	−0.011 (3)
C207	0.061 (5)	0.047 (4)	0.063 (5)	−0.004 (3)	−0.005 (4)	−0.002 (3)
C208	0.070 (5)	0.046 (4)	0.042 (4)	−0.014 (3)	0.018 (4)	−0.005 (3)
C209	0.037 (4)	0.047 (4)	0.067 (5)	−0.003 (3)	0.007 (3)	−0.009 (3)
C210	0.067 (5)	0.046 (4)	0.051 (4)	−0.009 (3)	−0.005 (4)	−0.002 (3)
C211	0.068 (5)	0.046 (4)	0.059 (5)	−0.011 (3)	0.010 (4)	0.000 (3)
C301	0.051 (4)	0.047 (4)	0.047 (4)	−0.007 (3)	−0.005 (3)	0.002 (3)
C302	0.059 (4)	0.046 (4)	0.059 (4)	−0.001 (4)	−0.004 (4)	−0.006 (3)
C303	0.049 (4)	0.070 (4)	0.042 (4)	−0.002 (3)	0.006 (3)	0.002 (3)
C304	0.044 (4)	0.053 (4)	0.056 (4)	0.005 (3)	−0.012 (3)	−0.003 (3)
C305	0.046 (4)	0.071 (5)	0.042 (4)	0.013 (3)	−0.001 (3)	−0.008 (3)
C401	0.066 (4)	0.045 (4)	0.069 (5)	−0.007 (3)	0.004 (4)	−0.010 (3)
C402	0.055 (4)	0.039 (3)	0.065 (4)	−0.003 (3)	−0.002 (3)	−0.004 (3)

Geometric parameters (Å, º)

Cl41—C402	1.768 (6)	C304—C305	1.532 (8)
Cl42—C402	1.765 (6)	C401—C402	1.512 (8)
Cl43—C402	1.759 (6)	N201—H1	0.950
O101—C101	1.462 (7)	C102—H9	0.950
O101—C105	1.344 (8)	C102—H10	0.950
O102—C105	1.221 (8)	C102—H11	0.950
O201—C202	1.251 (8)	C103—H6	0.950
O202—C203	1.440 (7)	C103—H7	0.950
O202—C205	1.412 (6)	C103—H8	0.950
O301—C302	1.197 (8)	C104—H22	0.950
O401—C302	1.375 (8)	C104—H23	0.950
O401—C401	1.437 (7)	C104—H24	0.950
N201—C105	1.364 (8)	C201—H12	0.950
N201—C201	1.448 (7)	C203—H4	0.950
N301—C202	1.334 (8)	C204—H25	0.950
N301—C301	1.457 (7)	C204—H26	0.950
N301—C305	1.478 (7)	C204—H27	0.950
C101—C102	1.509 (9)	C205—H13	0.950
C101—C103	1.528 (9)	C205—H14	0.950
C101—C104	1.498 (9)	C207—H31	0.950
C201—C202	1.523 (9)	C208—H21	0.950
C201—C203	1.516 (8)	C209—H2	0.950
C203—C204	1.499 (9)	C210—H30	0.950
C205—C206	1.492 (9)	C211—H3	0.950
C206—C207	1.360 (10)	C301—H5	0.950
C206—C211	1.358 (10)	C303—H28	0.950
C207—C208	1.375 (10)	C303—H29	0.950
C208—C209	1.369 (9)	C304—H15	0.950
C209—C210	1.381 (10)	C304—H16	0.950
C210—C211	1.378 (10)	C305—H17	0.950
C301—C302	1.488 (9)	C305—H18	0.950
C301—C303	1.517 (8)	C401—H19	0.950
C303—C304	1.545 (8)	C401—H20	0.950
C101—O101—C105	120.6 (4)	C101—C103—H8	109.1
C203—O202—C205	115.5 (4)	H6—C103—H7	109.5
C302—O401—C401	117.3 (4)	H6—C103—H8	109.5
C105—N201—C201	119.8 (5)	H7—C103—H8	109.5
C202—N301—C301	119.3 (5)	C101—C104—H22	109.2
C202—N301—C305	127.1 (5)	C101—C104—H23	110.3
C301—N301—C305	113.3 (4)	C101—C104—H24	108.9
O101—C101—C102	111.7 (5)	H22—C104—H23	109.5
O101—C101—C103	102.9 (4)	H22—C104—H24	109.5
O101—C101—C104	109.5 (5)	H23—C104—H24	109.5
C102—C101—C103	112.7 (5)	N201—C201—H12	108.9
C102—C101—C104	110.4 (5)	C202—C201—H12	109.6
C103—C101—C104	109.5 (5)	C203—C201—H12	109.6
O101—C105—O102	127.2 (6)	O202—C203—H4	108.6
O101—C105—N201	109.5 (5)	C201—C203—H4	108.6
O102—C105—N201	123.3 (6)	C204—C203—H4	109.3
N201—C201—C202	109.0 (4)	C203—C204—H25	107.7
N201—C201—C203	108.7 (4)	C203—C204—H26	110.8
C202—C201—C203	111.0 (5)	C203—C204—H27	109.9
O201—C202—N301	119.5 (5)	H25—C204—H26	109.5
O201—C202—C201	122.4 (5)	H25—C204—H27	109.5
N301—C202—C201	117.8 (5)	H26—C204—H27	109.5
O202—C203—C201	104.6 (4)	O202—C205—H13	110.5
O202—C203—C204	113.0 (5)	O202—C205—H14	108.9
C201—C203—C204	112.6 (5)	C206—C205—H13	109.8
O202—C205—C206	108.7 (4)	C206—C205—H14	109.6
C205—C206—C207	121.2 (6)	H13—C205—H14	109.5
C205—C206—C211	121.9 (6)	C206—C207—H31	118.2
C207—C206—C211	116.9 (6)	C208—C207—H31	120.3
C206—C207—C208	121.5 (6)	C207—C208—H21	119.9
C207—C208—C209	120.6 (6)	C209—C208—H21	119.5
C208—C209—C210	119.0 (6)	C208—C209—H2	120.3
C209—C210—C211	118.2 (6)	C210—C209—H2	120.7
C206—C211—C210	123.7 (6)	C209—C210—H30	120.5
N301—C301—C302	113.3 (5)	C211—C210—H30	121.2
N301—C301—C303	103.6 (4)	C206—C211—H3	117.4
C302—C301—C303	111.6 (5)	C210—C211—H3	118.9
O301—C302—O401	122.7 (6)	N301—C301—H5	109.7
O301—C302—C301	126.6 (6)	C302—C301—H5	108.9
O401—C302—C301	110.5 (5)	C303—C301—H5	109.6
C301—C303—C304	105.2 (4)	C301—C303—H28	108.8
C303—C304—C305	102.6 (4)	C301—C303—H29	111.9
N301—C305—C304	102.0 (4)	C304—C303—H28	109.8
O401—C401—C402	107.7 (5)	C304—C303—H29	111.5
Cl41—C402—Cl42	107.6 (3)	H28—C303—H29	109.5
Cl41—C402—Cl43	109.3 (3)	C303—C304—H15	110.4
Cl41—C402—C401	112.1 (4)	C303—C304—H16	112.0
Cl42—C402—Cl43	109.2 (3)	C305—C304—H15	110.4
Cl42—C402—C401	111.0 (4)	C305—C304—H16	111.8
Cl43—C402—C401	107.7 (4)	H15—C304—H16	109.5
C105—N201—H1	121.1	N301—C305—H17	111.4
C201—N201—H1	119.1	N301—C305—H18	111.4
C101—C102—H9	107.3	C304—C305—H17	112.1
C101—C102—H10	111.3	C304—C305—H18	110.4
C101—C102—H11	109.8	H17—C305—H18	109.5
H9—C102—H10	109.5	O401—C401—H19	110.1
H9—C102—H11	109.5	O401—C401—H20	110.0
H10—C102—H11	109.5	C402—C401—H19	109.7
C101—C103—H6	110.7	C402—C401—H20	109.9
C101—C103—H7	108.6	H19—C401—H20	109.5
C101—O101—C105—O102	3.2 (10)	N201—C201—C203—O202	48.1 (6)
C101—O101—C105—N201	−177.5 (5)	N201—C201—C203—C204	−74.9 (6)
C105—O101—C101—C102	−59.6 (7)	C202—C201—C203—O202	−71.8 (6)
C105—O101—C101—C103	179.2 (5)	C202—C201—C203—C204	165.2 (5)
C105—O101—C101—C104	62.9 (7)	C203—C201—C202—O201	97.2 (6)
C203—O202—C205—C206	−179.6 (5)	C203—C201—C202—N301	−76.2 (7)
C205—O202—C203—C201	160.1 (4)	O202—C205—C206—C207	−108.3 (6)
C205—O202—C203—C204	−77.1 (6)	O202—C205—C206—C211	69.5 (7)
C302—O401—C401—C402	122.3 (5)	C205—C206—C207—C208	178.6 (5)
C401—O401—C302—O301	3.7 (9)	C205—C206—C211—C210	−177.0 (5)
C401—O401—C302—C301	−172.5 (5)	C207—C206—C211—C210	1.0 (9)
C105—N201—C201—C202	−68.8 (6)	C211—C206—C207—C208	0.6 (9)
C105—N201—C201—C203	170.0 (5)	C206—C207—C208—C209	−2.0 (9)
C201—N201—C105—O101	162.6 (5)	C207—C208—C209—C210	1.7 (9)
C201—N201—C105—O102	−18.1 (9)	C208—C209—C210—C211	−0.2 (6)
C202—N301—C301—C302	−63.5 (7)	C209—C210—C211—C206	−1.2 (9)
C202—N301—C301—C303	175.4 (5)	N301—C301—C302—O301	150.7 (6)
C301—N301—C202—O201	1.0 (8)	N301—C301—C302—O401	−33.3 (7)
C301—N301—C202—C201	174.6 (5)	N301—C301—C303—C304	−23.0 (6)
C202—N301—C305—C304	−152.7 (5)	C302—C301—C303—C304	−145.3 (5)
C305—N301—C202—O201	174.2 (5)	C303—C301—C302—O301	−92.8 (8)
C305—N301—C202—C201	−12.1 (9)	C303—C301—C302—O401	83.2 (6)
C301—N301—C305—C304	20.9 (6)	C301—C303—C304—C305	35.8 (6)
C305—N301—C301—C302	122.4 (5)	C303—C304—C305—N301	−33.5 (5)
C305—N301—C301—C303	1.3 (6)	O401—C401—C402—Cl41	55.1 (5)
N201—C201—C202—O201	−22.5 (8)	O401—C401—C402—Cl42	−65.2 (5)
N201—C201—C202—N301	164.0 (5)	O401—C401—C402—Cl43	175.3 (4)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
N201—H1···O202	0.95	2.25	2.601 (6)	101