tert-Butoxy­carbonyl-L-leucyl-L-valine trichloro­ethyl ester (Boc-L-Leu-L-Val-OTce)

The title compound, C₁₈H₃₁Cl₃N₂O₅, an enanti­opure dipeptide trichloro­ethyl ester, is one of two starting fragments in the synthesis of cyclo­sporin O analogs. In the crystal structure, mol­ecules are linked by N—H...O=C hydrogen bonds, forming a β-spiral assembly along the c axis.

Key indicators

• Single-crystal X-ray study
• T = 173 K
• Mean [sigma](C-C) = 0.007 Å
• R factor = 0.035
• wR factor = 0.087
• Data-to-parameter ratio = 15.3

checkCIF/PLATON results

No syntax errors found



Alert level A
PLAT220_ALERT_2_A Large Non-Solvent    C     Ueq(max)/Ueq(min) ...       5.81 Ratio

Alert level B
PLAT026_ALERT_3_B Ratio Observed / Unique Reflections too Low ....         36 Perc.
PLAT222_ALERT_3_B Large Non-Solvent    H     Ueq(max)/Ueq(min) ...       4.47 Ratio
PLAT230_ALERT_2_B Hirshfeld Test Diff for    C11    -   C14     ..       9.00 su
PLAT360_ALERT_2_B Short  C(sp3)-C(sp3) Bond  C33    -   C35    ...       1.31 Ang.

Alert level C
PLAT230_ALERT_2_C Hirshfeld Test Diff for    O102   -   C15     ..       6.40 su
PLAT242_ALERT_2_C Check Low       Ueq as Compared to Neighbors for        C11
PLAT242_ALERT_2_C Check Low       Ueq as Compared to Neighbors for        C24
PLAT242_ALERT_2_C Check Low       Ueq as Compared to Neighbors for        C42
PLAT340_ALERT_3_C Low Bond Precision on C-C bonds (x 1000) Ang ...          7
PLAT390_ALERT_3_C Deviating Methyl C35     X-C-H Bond Angle ......     102.00 Deg.
PLAT431_ALERT_2_C Short Inter HL..A Contact  CL402  ..  O301    ..       3.16 Ang.
PLAT720_ALERT_4_C Number of Unusual/Non-Standard Label(s) ........          3

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           68.21
           From the CIF: _reflns_number_total               4352
           Count of symmetry unique reflns         2225
           Completeness (_total/calc)            195.60%
           TEST3: Check Friedels for noncentro structure
           Estimate of Friedel pairs measured      2127
           Fraction of Friedel pairs measured     0.956
           Are heavy atom types Z>Si present        yes

   1 ALERT level A = In general: serious problem
   4 ALERT level B = Potentially serious problem
   8 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
   8 ALERT type 2 Indicator that the structure model may be wrong or deficient
   4 ALERT type 3 Indicator that the structure quality may be low
   2 ALERT type 4 Improvement, methodology, query or suggestion

---

Computing details

Data collection: RAPID-AUTO (Rigaku, 2003); cell refinement: RAPID-AUTO; data reduction: CrystalStructure (Rigaku, 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.

tert-Butoxycarbonyl-L-Leucyll-L-Valine Trichloroethyl Ester (Boc-L-Leu-L-Val-OTce)

Crystal data

C18H31Cl3N2O5	Dx = 1.292 Mg m^−3
Mr = 461.81	Melting point = 377–379 K
Hexagonal, P65	Cu Kα radiation, λ = 1.54187 Å
Hall symbol: P 65	Cell parameters from 30511 reflections
a = 12.245 (5) Å	θ = 4.2–62.2°
c = 27.416 (13) Å	µ = 3.75 mm^−1
V = 3560 (3) Å^3	T = 173 K
Z = 6	Needle, colorless
F(000) = 1464.00	0.20 × 0.01 × 0.01 mm
? # Insert any comments here.

Data collection

Rigaku RAXIS-RAPID diffractometer	Rint = 0.068
Detector resolution: 10.00 pixels mm^-1	θmax = 68.2°
ω scans	h = −14→14
32841 measured reflections	k = −14→14
4352 independent reflections	l = −32→32
1558 reflections with F^2 > 2σ(F^2)

Refinement

Refinement on F^2	w = 4Fo^2/[0.0002Fo^2 + 0.2σ(Fo^2) + 0.1]
R[F^2 > 2σ(F^2)] = 0.035	(Δ/σ)max < 0.001
wR(F^2) = 0.087	Δρmax = 1.17 e Å^−3
S = 0.97	Δρmin = −0.93 e Å^−3
4352 reflections	Absolute structure: Flack (1983), 2123 Friedel pairs
285 parameters	Absolute structure parameter: 0.015 (15)
All H-atom parameters refined

Special details

Experimental. ? #Insert any special details here.

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
Cl401	0.60861 (13)	0.20699 (12)	0.86581 (6)	0.0852 (5)
Cl402	0.83672 (13)	0.44215 (12)	0.85070 (5)	0.0745 (4)
Cl403	0.81787 (13)	0.28960 (12)	0.93194 (6)	0.0891 (5)
O101	1.1143 (2)	1.2369 (2)	0.87504 (9)	0.0424 (8)
O102	1.0485 (2)	1.1818 (2)	0.95364 (10)	0.0553 (9)
O201	0.8629 (2)	0.8101 (2)	0.88992 (9)	0.0453 (9)
O301	0.6407 (2)	0.5842 (2)	0.95051 (12)	0.0569 (10)
O401	0.7734 (2)	0.5107 (2)	0.94583 (11)	0.0587 (10)
N201	0.9319 (2)	1.0687 (2)	0.88961 (11)	0.0360 (9)
N301	0.8433 (3)	0.8209 (3)	0.97106 (11)	0.0365 (10)
C11	1.2240 (4)	1.3582 (4)	0.88841 (17)	0.0483 (14)
C12	1.1798 (4)	1.4409 (4)	0.9101 (2)	0.0814 (19)
C13	1.2840 (4)	1.4074 (4)	0.83940 (18)	0.0781 (18)
C14	1.3115 (4)	1.3405 (4)	0.92183 (17)	0.0790 (19)
C15	1.0329 (3)	1.1647 (3)	0.91022 (16)	0.0378 (13)
C21	0.8321 (3)	0.9759 (3)	0.91912 (12)	0.0369 (12)
C22	0.8470 (3)	0.8621 (3)	0.92579 (14)	0.0333 (12)
C23	0.7060 (3)	0.9347 (3)	0.89579 (13)	0.0412 (13)
C24	0.5939 (4)	0.8571 (4)	0.92894 (17)	0.0529 (14)
C25	0.5827 (4)	0.9388 (4)	0.96814 (16)	0.0679 (18)
C26	0.4744 (4)	0.7954 (5)	0.8980 (2)	0.111 (2)
C31	0.8525 (4)	0.7096 (4)	0.97878 (16)	0.0475 (15)
C32	0.7423 (5)	0.5990 (4)	0.95651 (16)	0.0470 (15)
C33	0.8691 (6)	0.6886 (5)	1.0327 (2)	0.103 (2)
C34	0.9849 (5)	0.7957 (5)	1.0538 (2)	0.112 (2)
C35	0.7698 (7)	0.6264 (7)	1.0607 (2)	0.193 (3)
C41	0.6773 (4)	0.3997 (4)	0.92419 (18)	0.0642 (18)
C42	0.7343 (4)	0.3390 (4)	0.89523 (18)	0.0587 (16)
H121	1.2489	1.5177	0.9191	0.090*
H122	1.1327	1.4542	0.8861	0.090*
H123	1.1299	1.4029	0.9380	0.090*
H131	1.3051	1.3516	0.8248	0.079*
H132	1.2273	1.4161	0.8190	0.079*
H133	1.3564	1.4856	0.8435	0.079*
H141	1.2731	1.3091	0.9525	0.083*
H142	1.3321	1.2842	0.9073	0.083*
H143	1.3845	1.4180	0.9265	0.082*
H201	0.9262	1.0614	0.8550	0.038*
H211	0.8349	1.0103	0.9504	0.041*
H231	0.7033	1.0063	0.8861	0.047*
H232	0.6987	0.8867	0.8678	0.047*
H241	0.6038	0.7943	0.9441	0.060*
H251	0.6554	0.9752	0.9875	0.082*
H252	0.5728	1.0018	0.9532	0.082*
H253	0.5132	0.8894	0.9882	0.082*
H261	0.4641	0.8579	0.8827	0.118*
H262	0.4813	0.7449	0.8737	0.118*
H263	0.4050	0.7463	0.9182	0.118*
H301	0.8357	0.8640	0.9982	0.041*
H311	0.9222	0.7209	0.9606	0.057*
H331	0.8916	0.6266	1.0306	0.099*
H341	1.0025	0.7757	1.0851	0.128*
H342	1.0539	0.8198	1.0329	0.128*
H343	0.9683	0.8617	1.0567	0.127*
H351	0.7422	0.6843	1.0642	0.170*
H352	0.7065	0.5530	1.0462	0.170*
H353	0.7894	0.6077	1.0920	0.170*
H411	0.6276	0.3446	0.9492	0.077*
H412	0.6274	0.4181	0.9036	0.077*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Cl401	0.1034 (11)	0.0575 (8)	0.0906 (10)	0.0371 (8)	−0.0058 (9)	−0.0151 (7)
Cl402	0.0947 (10)	0.0741 (9)	0.0612 (7)	0.0470 (8)	0.0238 (7)	0.0145 (7)
Cl403	0.1223 (13)	0.0673 (9)	0.0902 (10)	0.0568 (9)	−0.0098 (9)	0.0100 (8)
O101	0.0398 (17)	0.0307 (17)	0.0330 (15)	−0.0003 (14)	−0.0011 (14)	−0.0010 (13)
O102	0.056 (2)	0.052 (2)	0.0266 (17)	0.0036 (17)	−0.0074 (14)	−0.0023 (16)
O201	0.068 (2)	0.0373 (17)	0.0338 (15)	0.0282 (16)	0.0124 (15)	−0.0013 (14)
O301	0.039 (2)	0.0407 (19)	0.081 (2)	0.0129 (17)	0.0064 (18)	−0.0004 (16)
O401	0.062 (2)	0.050 (2)	0.066 (2)	0.0284 (19)	0.0020 (17)	−0.0130 (17)
N201	0.043 (2)	0.0240 (18)	0.0272 (18)	0.0060 (17)	0.0028 (17)	0.0016 (15)
N301	0.048 (2)	0.035 (2)	0.0215 (17)	0.0165 (18)	0.0056 (16)	0.0021 (16)
C11	0.036 (2)	0.035 (2)	0.053 (3)	0.003 (2)	−0.003 (2)	0.002 (2)
C12	0.063 (3)	0.031 (2)	0.130 (5)	0.009 (2)	0.007 (3)	−0.019 (3)
C13	0.063 (3)	0.060 (3)	0.074 (3)	0.003 (3)	0.006 (3)	0.005 (2)
C14	0.050 (3)	0.069 (3)	0.087 (4)	0.007 (2)	−0.001 (3)	−0.003 (3)
C15	0.037 (2)	0.029 (2)	0.042 (2)	0.012 (2)	0.000 (2)	0.007 (2)
C21	0.043 (2)	0.033 (2)	0.027 (2)	0.013 (2)	0.008 (2)	−0.0028 (19)
C22	0.034 (2)	0.026 (2)	0.033 (2)	0.010 (2)	0.011 (2)	0.001 (2)
C23	0.041 (2)	0.033 (2)	0.043 (2)	0.013 (2)	0.006 (2)	−0.001 (2)
C24	0.045 (2)	0.037 (2)	0.068 (3)	0.015 (2)	0.013 (2)	0.008 (2)
C25	0.066 (3)	0.071 (3)	0.067 (3)	0.034 (3)	0.022 (2)	0.004 (3)
C26	0.044 (3)	0.129 (5)	0.121 (5)	0.014 (3)	0.009 (3)	−0.008 (4)
C31	0.047 (3)	0.045 (3)	0.050 (3)	0.023 (2)	0.007 (2)	0.013 (2)
C32	0.050 (3)	0.042 (3)	0.044 (2)	0.019 (2)	0.012 (2)	0.011 (2)
C33	0.109 (5)	0.057 (4)	0.080 (4)	−0.004 (3)	−0.034 (4)	0.027 (3)
C34	0.129 (5)	0.063 (3)	0.127 (5)	0.035 (4)	−0.067 (4)	0.006 (3)
C35	0.200 (8)	0.170 (8)	0.054 (4)	−0.024 (6)	0.010 (5)	0.019 (5)
C41	0.076 (3)	0.048 (3)	0.068 (3)	0.030 (3)	0.009 (3)	−0.014 (2)
C42	0.076 (3)	0.047 (3)	0.050 (2)	0.029 (2)	0.010 (2)	0.006 (2)

Geometric parameters (Å, º)

Cl401—C42	1.773 (4)	C12—H121	0.932
Cl402—C42	1.753 (4)	C12—H122	0.940
Cl403—C42	1.744 (6)	C12—H123	0.944
O101—C11	1.466 (4)	C13—H131	0.934
O101—C15	1.351 (4)	C13—H132	0.938
O102—C15	1.207 (5)	C13—H133	0.931
O201—C22	1.239 (5)	C14—H141	0.947
O301—C32	1.175 (7)	C14—H142	0.934
O401—C32	1.346 (8)	C14—H143	0.931
O401—C41	1.409 (4)	C21—H211	0.947
N201—C15	1.332 (4)	C23—H231	0.932
N201—C21	1.432 (4)	C23—H232	0.944
N301—C22	1.332 (5)	C24—H241	0.934
N301—C31	1.439 (7)	C25—H251	0.937
C11—C12	1.489 (8)	C25—H252	0.934
C11—C13	1.505 (6)	C25—H253	0.937
C11—C14	1.506 (7)	C26—H261	0.934
C21—C22	1.505 (7)	C26—H262	0.941
C21—C23	1.506 (5)	C26—H263	0.937
C23—C24	1.519 (5)	C31—H311	0.936
C24—C25	1.520 (7)	C33—H331	0.930
C24—C26	1.525 (6)	C34—H341	0.948
C31—C32	1.483 (5)	C34—H342	0.938
C31—C33	1.531 (7)	C34—H343	0.930
C33—C34	1.485 (7)	C35—H351	0.931
C33—C35	1.312 (9)	C35—H352	0.934
C41—C42	1.480 (8)	C35—H353	0.947
N201—H201	0.951	C41—H411	0.941
N301—H301	0.943	C41—H412	0.937
C11—O101—C15	119.1 (3)	H132—C13—H133	109.5
C32—O401—C41	115.6 (4)	C11—C14—H141	110.7
C15—N201—C21	120.5 (3)	C11—C14—H142	108.7
C22—N301—C31	119.5 (3)	C11—C14—H143	109.1
O101—C11—C12	109.2 (3)	H141—C14—H142	110.0
O101—C11—C13	101.5 (3)	H141—C14—H143	108.8
O101—C11—C14	111.3 (3)	H142—C14—H143	109.5
C12—C11—C13	110.7 (4)	N201—C21—H211	109.3
C12—C11—C14	112.5 (4)	C22—C21—H211	107.9
C13—C11—C14	111.1 (4)	C23—C21—H211	109.7
O101—C15—O102	126.1 (3)	C21—C23—H231	108.5
O101—C15—N201	109.3 (3)	C21—C23—H232	108.4
O102—C15—N201	124.6 (3)	C24—C23—H231	108.2
N201—C21—C22	110.6 (3)	C24—C23—H232	108.9
N201—C21—C23	110.6 (3)	H231—C23—H232	108.5
C22—C21—C23	108.7 (3)	C23—C24—H241	109.4
O201—C22—N301	122.0 (4)	C25—C24—H241	108.6
O201—C22—C21	120.2 (3)	C26—C24—H241	109.1
N301—C22—C21	117.8 (3)	C24—C25—H251	109.7
C21—C23—C24	114.2 (3)	C24—C25—H252	109.0
C23—C24—C25	111.2 (3)	C24—C25—H253	110.0
C23—C24—C26	108.7 (3)	H251—C25—H252	109.9
C25—C24—C26	109.8 (5)	H251—C25—H253	108.3
N301—C31—C32	109.7 (4)	H252—C25—H253	109.9
N301—C31—C33	112.3 (4)	C24—C26—H261	109.4
C32—C31—C33	112.4 (3)	C24—C26—H262	109.9
O301—C32—O401	123.2 (3)	C24—C26—H263	109.1
O301—C32—C31	127.5 (5)	H261—C26—H262	108.3
O401—C32—C31	109.2 (5)	H261—C26—H263	109.9
C31—C33—C34	112.1 (4)	H262—C26—H263	110.2
C31—C33—C35)	120.1 (6)	N301—C31—H311	106.2
C34—C33—C35)	118.9 (5)	C32—C31—H311	105.2
O401—C41—C42	109.5 (4)	C33—C31—H311	110.6
Cl401—C42—Cl402	108.8 (2)	C31—C33—H331	101.1
Cl401—C42—Cl403	109.8 (2)	C34—C33—H331	101.7
Cl401—C42—C41	106.8 (3)	C35—C33—H331	97.4
Cl402—C42—Cl403	108.6 (2)	C33—C34—H341	111.4
Cl402—C42—C41	111.0 (3)	C33—C34—H342	110.7
Cl403—C42—C41	111.7 (3)	C33—C34—H343	105.9
C15—N201—H201	119.8	H341—C34—H342	110.4
C21—N201—H201	119.7	H341—C34—H343	108.9
C22—N301—H301	121.2	H342—C34—H343	109.5
C31—N301—H301	119.4	C33—C35—H351	101.6
C11—C12—H121	109.7	C33—C35—H352	113.0
C11—C12—H122	107.6	C33—C35—H353	113.4
C11—C12—H123	110.7	H351—C35—H352	109.5
H121—C12—H122	109.7	H351—C35—H353	108.9
H121—C12—H123	108.6	H352—C35—H353	110.0
H122—C12—H123	110.5	O401—C41—H411	108.3
C11—C13—H131	110.4	O401—C41—H412	110.6
C11—C13—H132	109.7	C42—C41—H411	109.2
C11—C13—H133	109.1	C42—C41—H412	109.0
H131—C13—H132	108.6	H411—C41—H412	110.2
H131—C13—H133	109.5
C11—O101—C15—O102	−9.9 (8)	N201—C21—C23—C24	−168.2 (4)
C11—O101—C15—N201	171.1 (4)	C22—C21—C23—C24	70.2 (4)
C15—O101—C11—C12	−61.0 (5)	C23—C21—C22—O201	70.5 (4)
C15—O101—C11—C13	−177.9 (4)	C23—C21—C22—N301	−109.8 (3)
C15—O101—C11—C14	63.7 (5)	C21—C23—C24—C25	72.6 (5)
C32—O401—C41—C42	154.9 (4)	C21—C23—C24—C26	−166.4 (4)
C41—O401—C32—O301	3.3 (6)	N301—C31—C32—O301	−28.3 (6)
C41—O401—C32—C31	−179.8 (3)	N301—C31—C32—O401	155.1 (3)
C15—N201—C21—C22	−96.9 (4)	N301—C31—C33—C34	−59.9 (7)
C15—N201—C21—C23	142.6 (4)	N301—C31—C33—C35	87.0 (7)
C21—N201—C15—O101	178.5 (4)	C32—C31—C33—C34	175.8 (6)
C21—N201—C15—O102	−0.4 (7)	C32—C31—C33—C35	−37.3 (10)
C22—N301—C31—C32	−63.9 (4)	C33—C31—C32—O301	97.5 (6)
C22—N301—C31—C33	170.3 (3)	C33—C31—C32—O401	−79.2 (5)
C31—N301—C22—O201	−2.6 (5)	O401—C41—C42—Cl401	−175.9 (3)
C31—N301—C22—C21	177.7 (3)	O401—C41—C42—Cl402	−57.5 (4)
N201—C21—C22—O201	−51.1 (4)	O401—C41—C42—Cl403	64.0 (4)
N201—C21—C22—N301	128.6 (3)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
N201—H201···O102^i	0.95	1.98	2.902 (4)	162
N301—H301···O201^ii	0.94	2.01	2.947 (4)	177

Symmetry codes: (i) x−y+1, x, z−1/6; (ii) y, −x+y+1, z+1/6.