A short depsipeptide: tert-butoxy­carbonyl-L-alanyl-L-lactic acid benzyl ester (Boc-L-Ala-L-Lac-OBzl)

The title compound, C₁₈H₂₅N₁O₆, crystallizes in an extended sheet-like conformation. In the crystal structure, independent mol­ecules are linked by an N—H...O=C hydrogen bond, yielding an infinite arrangement.

Key indicators

• Single-crystal X-ray study
• T = 173 K
• Mean [sigma](C-C) = 0.009 Å
• R factor = 0.070
• wR factor = 0.182
• Data-to-parameter ratio = 9.1

checkCIF/PLATON results

No syntax errors found



Alert level A
PLAT029_ALERT_3_A _diffrn_measured_fraction_theta_full Low .......       0.92

Author Response: This is due to the data collection by rotation around a spindle axis on our image-plate system.

PLAT201_ALERT_2_A Isotropic non-H Atoms in Main Residue(s) .......         12

Author Response: Because of the limited numbers of observed reflections. Even at the low temperature condition (173 K), diffractions from the crystal of (I) were too weak to collect enough numbers. Therefore only main-cain atoms were refefined anisotropically.

Alert level C
REFLT03_ALERT_1_C  Reflection count < 95% complete
           From the CIF: _diffrn_reflns_theta_max           68.15
           From the CIF: _diffrn_reflns_theta_full           0.00
           From the CIF: _reflns_number_total               1747
           TEST2: Reflns within _diffrn_reflns_theta_max
           Count of symmetry unique reflns         1905
           Completeness (_total/calc)             91.71%

Author Response: All the Friedel pairs have been averaged during the refinement process.

PLAT022_ALERT_3_C Ratio Unique / Expected Reflections too Low ....       0.92
PLAT152_ALERT_1_C Supplied and Calc Volume s.u. Inconsistent .....          ?
PLAT242_ALERT_2_C Check Low    U(eq) as Compared to Neighbors ....       C101

Author Response: It is due to the difference of thermal mobility. The atoms located at chain-ends 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: The chain end atoms (-OEt) often show lower bond precision due to their higher thermal mobility compared with the atoms located inside of the chain.

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           68.15
           From the CIF: _reflns_number_total               1747
           Count of symmetry unique reflns         1905
           Completeness (_total/calc)             91.71%
           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

Author Response: All the Friedel pairs have been averaged during the refinement process.

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

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

---

Computing details

Data collection: RAPID-AUTO (Rigaku/MSC and Rigaku, 2003); cell refinement: RAPID-AUTO; data reduction: CrystalStructure (Rigaku/MSC and Rigaku, 2003); program(s) used to solve structure: SIR2002 (Burla et al., 2003); program(s) used to refine structure: CRYSTALS (Watkin et al., 1996); molecular graphics: ORTEP (Johnson, 1965); software used to prepare material for publication: CrystalStructure.

tert-butoxycarbonyl-L-alanyl-L-lactic acid benzyl ester

Crystal data

C18H25NO6	F(000) = 376.00
Mr = 351.40	Dx = 1.200 Mg m^−3
Monoclinic, P21	Melting point = 356–359 K
Hall symbol: P 2yb	Cu Kα radiation, λ = 1.54180 Å
a = 10.365 (6) Å	Cell parameters from 4037 reflections
b = 8.827 (5) Å	θ = 4.2–67.5°
c = 11.001 (6) Å	µ = 0.75 mm^−1
β = 104.93 (2)°	T = 173 K
V = 972.4 (9) Å^3	Prism, colorless
Z = 2	0.40 × 0.30 × 0.05 mm

Data collection

Rigaku R-AXIS RAPID diffractometer	1624 reflections with F^2 > 2σ(F^2)
Detector resolution: 10.00 pixels mm^-1	Rint = 0.029
ω scans	θmax = 68.2°
Absorption correction: part of the refinement model (ΔF) (DIFABS; Walker & Stuart, 1983)	h = −12→12
Tmin = 0.789, Tmax = 0.963	k = −10→10
15424 measured reflections	l = −13→12
1747 independent reflections

Refinement

Refinement on F^2	All H-atom parameters refined
R[F^2 > 2σ(F^2)] = 0.070	w = 1/[0.005Fo^2 + 20σ(Fo^2) + 0.5]/(4Fo^2)
wR(F^2) = 0.182	(Δ/σ)max < 0.001
S = 0.94	Δρmax = 0.37 e Å^−3
1747 reflections	Δρmin = −0.33 e Å^−3
191 parameters

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
O101	0.5520 (4)	−0.0931 (4)	−0.3100 (4)	0.053 (1)
O102	0.7257 (3)	0.0772 (5)	−0.2773 (4)	0.057 (1)
O201	0.7025 (4)	0.1609 (5)	0.0288 (4)	0.067 (1)
O301	0.7833 (3)	0.3707 (4)	−0.0412 (3)	0.0421 (9)
O302	0.6946 (4)	0.5067 (6)	0.1399 (3)	0.067 (1)
O401	0.8731 (3)	0.4292 (4)	0.2888 (3)	0.051 (1)
N201	0.5336 (4)	0.1291 (5)	−0.2220 (4)	0.043 (1)
C101	0.6277 (6)	−0.2199 (7)	−0.3459 (6)	0.059 (1)*
C102	0.7330 (8)	−0.269 (1)	−0.2301 (8)	0.094 (2)*
C103	0.6859 (8)	−0.180 (1)	−0.4514 (9)	0.100 (3)*
C104	0.5229 (8)	−0.339 (1)	−0.3827 (8)	0.092 (2)*
C105	0.6141 (5)	0.0391 (6)	−0.2699 (4)	0.041 (1)
C201	0.5827 (5)	0.2730 (6)	−0.1689 (5)	0.044 (1)
C202	0.6937 (5)	0.2577 (6)	−0.0509 (5)	0.046 (1)
C203	0.4675 (6)	0.3607 (7)	−0.1353 (6)	0.061 (1)*
C301	0.8771 (5)	0.3900 (6)	0.0782 (4)	0.044 (1)
C302	0.8027 (5)	0.4478 (6)	0.1707 (5)	0.045 (1)
C303	0.9790 (6)	0.5072 (7)	0.0617 (5)	0.059 (1)*
C401	0.8118 (6)	0.4949 (8)	0.3832 (5)	0.063 (2)
C402	0.9049 (5)	0.4682 (6)	0.5101 (5)	0.046 (1)*
C403	0.8688 (5)	0.3772 (6)	0.5981 (5)	0.047 (1)*
C404	0.9533 (6)	0.3579 (7)	0.7161 (5)	0.057 (1)*
C405	1.0769 (6)	0.4292 (7)	0.7477 (6)	0.060 (1)*
C406	1.1116 (7)	0.5229 (8)	0.6619 (6)	0.068 (2)*
C407	1.0270 (6)	0.5422 (8)	0.5438 (6)	0.064 (2)*
H1	0.6903	−0.2991	−0.1671	0.112*
H2	0.7820	−0.3526	−0.2501	0.112*
H3	0.7922	−0.1877	−0.1998	0.113*
H4	0.7329	−0.2648	−0.4720	0.120*
H5	0.6181	−0.1505	−0.5233	0.120*
H6	0.7461	−0.0985	−0.4247	0.120*
H7	0.4910	−0.3606	−0.3109	0.111*
H8	0.4511	−0.3048	−0.4493	0.111*
H9	0.5597	−0.4288	−0.4082	0.111*
H10	0.4458	0.0973	−0.2231	0.052*
H11	0.6134	0.3288	−0.2298	0.052*
H12	0.4978	0.4577	−0.1027	0.073*
H13	0.3964	0.3724	−0.2090	0.073*
H14	0.4370	0.3055	−0.0741	0.073*
H15	0.9213	0.2974	0.1068	0.053*
H16	1.0432	0.5258	0.1391	0.071*
H17	1.0230	0.4734	0.0009	0.070*
H18	0.9315	0.5979	0.0332	0.070*
H19	0.7973	0.6003	0.3682	0.076*
H20	0.7288	0.4461	0.3780	0.076*
H21	0.7839	0.3294	0.5772	0.056*
H22	0.9287	0.2924	0.7750	0.068*
H23	1.1347	0.4175	0.8295	0.072*
H24	1.1956	0.5728	0.6843	0.082*
H25	1.0545	0.6040	0.4844	0.077*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
O101	0.054 (2)	0.045 (2)	0.058 (2)	−0.003 (2)	0.012 (2)	−0.009 (2)
O102	0.038 (2)	0.057 (2)	0.077 (3)	0.001 (2)	0.017 (2)	0.001 (2)
O201	0.071 (3)	0.064 (3)	0.055 (2)	−0.010 (2)	−0.003 (2)	0.018 (2)
O301	0.043 (2)	0.047 (2)	0.036 (2)	−0.008 (2)	0.009 (1)	−0.007 (1)
O302	0.053 (2)	0.107 (3)	0.040 (2)	0.027 (2)	0.009 (2)	−0.005 (2)
O401	0.048 (2)	0.066 (2)	0.036 (2)	0.011 (2)	0.008 (2)	−0.005 (2)
N201	0.034 (2)	0.049 (2)	0.047 (2)	−0.011 (2)	0.011 (2)	−0.007 (2)
C105	0.035 (3)	0.049 (3)	0.036 (2)	−0.005 (2)	0.003 (2)	0.001 (2)
C201	0.038 (3)	0.051 (3)	0.041 (3)	−0.000 (2)	0.007 (2)	0.001 (2)
C202	0.043 (3)	0.052 (3)	0.043 (3)	0.006 (2)	0.011 (2)	−0.002 (3)
C301	0.041 (3)	0.059 (3)	0.032 (2)	0.003 (2)	0.007 (2)	−0.006 (2)
C302	0.043 (3)	0.051 (3)	0.040 (3)	0.004 (2)	0.012 (2)	−0.005 (2)
C401	0.058 (4)	0.094 (5)	0.037 (3)	0.023 (3)	0.011 (3)	−0.000 (3)

Geometric parameters (Å, º)

O101—C101	1.478 (8)	N201—H10	0.9500
O101—C105	1.351 (6)	C102—H1	0.9500
O102—C105	1.227 (6)	C102—H2	0.9500
O201—C202	1.211 (7)	C102—H3	0.9500
O301—C202	1.348 (7)	C103—H4	0.9501
O301—C301	1.429 (5)	C103—H5	0.9500
O302—C302	1.201 (7)	C103—H6	0.9500
O401—C302	1.326 (6)	C104—H7	0.9501
O401—C401	1.469 (7)	C104—H8	0.9500
N201—C105	1.353 (7)	C104—H9	0.9500
N201—C201	1.435 (7)	C201—H11	0.9500
C101—C102	1.513 (9)	C203—H12	0.9500
C101—C103	1.482 (9)	C203—H13	0.9499
C101—C104	1.491 (9)	C203—H14	0.9499
C201—C202	1.503 (6)	C301—H15	0.9500
C201—C203	1.546 (9)	C303—H16	0.9500
C301—C302	1.515 (8)	C303—H17	0.9500
C301—C303	1.522 (8)	C303—H18	0.9500
C401—C402	1.497 (7)	C401—H19	0.9500
C402—C403	1.381 (8)	C401—H20	0.9500
C402—C407	1.387 (8)	C403—H21	0.9500
C403—C404	1.377 (7)	C404—H22	0.9500
C404—C405	1.389 (8)	C405—H23	0.9500
C405—C406	1.371 (9)	C406—H24	0.9500
C406—C407	1.378 (8)	C407—H25	0.9501
O101—C101—C102	108.2 (5)	C101—C103—H5	110.8126
O101—C101—C103	112.4 (6)	C101—C103—H6	107.7609
O101—C101—C104	102.0 (5)	C101—C104—H7	107.3647
C105—O101—C101	120.0 (4)	C101—C104—H8	110.6768
O101—C105—O102	126.4 (5)	C101—C104—H9	110.3492
O101—C105—N201	110.2 (4)	H2—C102—H1	109.4672
O102—C105—N201	123.4 (5)	H3—C102—H1	109.4743
O201—C202—C201	125.9 (5)	H3—C102—H2	109.4727
O201—C202—O301	122.9 (4)	H5—C103—H4	109.4706
O301—C202—C201	111.2 (4)	H6—C103—H4	109.4722
C301—O301—C202	116.9 (4)	H6—C103—H5	109.4734
O301—C301—C302	108.3 (4)	H8—C104—H7	109.4695
O301—C301—C303	107.5 (4)	H9—C104—H7	109.4710
O302—C302—C301	123.7 (4)	H9—C104—H8	109.4749
O302—C302—O401	124.6 (5)	H11—C201—C202	109.4716
O401—C302—C301	111.6 (4)	H11—C201—C203	109.1917
C401—O401—C302	114.4 (4)	C201—C203—H12	109.9418
O401—C401—C402	107.8 (5)	C201—C203—H14	109.3372
C201—N201—C105	119.3 (4)	C201—C203—H13	109.1277
N201—C201—C202	112.6 (4)	H14—C203—H12	109.4714
N201—C201—C203	109.1 (4)	H13—C203—H12	109.4752
C103—C101—C102	112.2 (6)	H14—C203—H13	109.4729
C104—C101—C102	109.9 (6)	H15—C301—C302	110.7004
C104—C101—C103	111.6 (6)	H15—C301—C303	109.4643
C203—C201—C202	107.8 (4)	C301—C303—H16	110.9877
C303—C301—C302	109.9 (5)	C301—C303—H17	110.1540
C401—C402—C403	121.3 (5)	C301—C303—H18	107.2433
C401—C402—C407	120.0 (5)	H17—C303—H16	109.4695
C407—C402—C403	118.6 (5)	H18—C303—H16	109.4721
C402—C403—C404	120.8 (5)	H18—C303—H17	109.4765
C402—C407—C406	120.6 (6)	H19—C401—C402	110.5426
C403—C404—C405	120.0 (6)	H20—C401—C402	109.9041
C404—C405—C406	119.4 (5)	H20—C401—H19	109.4604
C405—C406—C407	120.5 (6)	C402—C403—H21	119.3187
O301—C301—H15	110.9564	C402—C407—H25	120.0817
O401—C401—H19	109.9480	H21—C403—C404	119.8455
O401—C401—H20	109.1913	C403—C404—H22	120.0760
H10—N201—C105	120.4366	H22—C404—C405	119.8395
H10—N201—C201	120.2967	C404—C405—H23	120.2310
N201—C201—H11	108.7045	C405—C406—H24	119.0989
C101—C102—H1	108.8443	H23—C405—C406	120.3234
C101—C102—H2	109.9174	C406—C407—H25	119.2730
C101—C102—H3	109.6494	H24—C406—C407	120.3841
O101—C105—N201—C201	177.4 (4)	C(102)—C(101)—C(103)—H(5)	179.4
C105—N201—C201—C202	−66.9 (6)	C(102)—C(101)—C(103)—H(6)	−60.8
N201—C201—C202—O301	145.9 (5)	C(104)—C(101)—C(103)—H(4)	−65.5
C201—C202—O301—C301	166.4 (4)	C(104)—C(101)—C(103)—H(5)	55.5
C202—O301—C301—C302	−69.3 (5)	C(104)—C(101)—C(103)—H(6)	175.3
O301—C301—C302—O401	162.7 (5)	O(101)—C(101)—C(104)—H(7)	−60.7
C301—C302—O401—C401	174.9 (4)	O(101)—C(101)—C(104)—H(8)	58.7
C(105)—O(101)—C(101)—C(102)	63.9 (7)	O(101)—C(101)—C(104)—H(9)	−180.0
C(105)—O(101)—C(101)—C(103)	−60.5 (6)	C(102)—C(101)—C(104)—H(7)	53.9
C(105)—O(101)—C(101)—C(104)	179.8 (4)	C(102)—C(101)—C(104)—H(8)	173.3
C(101)—O(101)—C(105)—O(102)	12.3 (7)	C(102)—C(101)—C(104)—H(9)	−65.3
C(101)—O(101)—C(105)—N(201)	−169.5 (4)	C(103)—C(101)—C(104)—H(7)	179.0
C(301)—O(301)—C(202)—O(201)	−11.5 (8)	C(103)—C(101)—C(104)—H(8)	−61.6
C(202)—O(301)—C(301)—C(303)	172.1 (4)	C(103)—C(101)—C(104)—H(9)	59.8
C(401)—O(401)—C(302)—O(302)	−3.2 (8)	H(11)—C(201)—C(202)—O(201)	−157.3
C(302)—O(401)—C(401)—C(402)	−178.4 (4)	H(11)—C(201)—C(202)—O(301)	24.8
C(201)—N(201)—C(105)—O(102)	−4.3 (7)	N(201)—C(201)—C(203)—H(12)	−178.0
C(105)—N(201)—C(201)—C(203)	173.5 (4)	N(201)—C(201)—C(203)—H(13)	−57.9
N(201)—C(201)—C(202)—O(201)	−36.3 (8)	N(201)—C(201)—C(203)—H(14)	61.8
C(203)—C(201)—C(202)—O(201)	84.1 (7)	C(202)—C(201)—C(203)—H(12)	59.4
C(203)—C(201)—C(202)—O(301)	−93.8 (5)	C(202)—C(201)—C(203)—H(13)	179.5
O(301)—C(301)—C(302)—O(302)	−19.1 (8)	C(202)—C(201)—C(203)—H(14)	−60.8
C(303)—C(301)—C(302)—O(302)	98.0 (6)	H(11)—C(201)—C(203)—H(12)	−59.4
C(303)—C(301)—C(302)—O(401)	−80.2 (5)	H(11)—C(201)—C(203)—H(13)	60.7
O(401)—C(401)—C(402)—C(403)	−115.6 (6)	H(11)—C(201)—C(203)—H(14)	−179.6
O(401)—C(401)—C(402)—C(407)	68.0 (8)	H(15)—C(301)—C(302)—O(302)	−141.0
C(401)—C(402)—C(403)—C(404)	−177.6 (5)	H(15)—C(301)—C(302)—O(401)	40.8
C(407)—C(402)—C(403)—C(404)	−1.2 (8)	O(301)—C(301)—C(303)—H(16)	178.9
C(401)—C(402)—C(407)—C(406)	177.7 (6)	O(301)—C(301)—C(303)—H(17)	−59.7
C(403)—C(402)—C(407)—C(406)	1.2 (9)	O(301)—C(301)—C(303)—H(18)	59.4
C(402)—C(403)—C(404)—C(405)	−0.6 (9)	C(302)—C(301)—C(303)—H(16)	61.3
C(403)—C(404)—C(405)—C(406)	2.3 (9)	C(302)—C(301)—C(303)—H(17)	−177.3
C(404)—C(405)—C(406)—C(407)	−2.3 (9)	C(302)—C(301)—C(303)—H(18)	−58.3
C(405)—C(406)—C(407)—C(402)	0.5 (9)	H(15)—C(301)—C(303)—H(16)	−60.5
C(202)—O(301)—C(301)—H(15)	52.4	H(15)—C(301)—C(303)—H(17)	60.9
C(302)—O(401)—C(401)—H(19)	−57.9	H(15)—C(301)—C(303)—H(18)	180.0
C(302)—O(401)—C(401)—H(20)	62.2	H(19)—C(401)—C(402)—C(403)	124.2
H(10)—N(201)—C(105)—O(101)	−2.3	H(19)—C(401)—C(402)—C(407)	−52.2
H(10)—N(201)—C(105)—O(102)	176.0	H(20)—C(401)—C(402)—C(403)	3.3
C(105)—N(201)—C(201)—H(11)	54.6	H(20)—C(401)—C(402)—C(407)	−173.1
H(10)—N(201)—C(201)—C(202)	112.8	C(401)—C(402)—C(403)—H(21)	1.0
H(10)—N(201)—C(201)—C(203)	−6.8	C(407)—C(402)—C(403)—H(21)	177.4
H(10)—N(201)—C(201)—H(11)	−125.7	C(401)—C(402)—C(407)—H(25)	−4.6
O(101)—C(101)—C(102)—H(1)	58.8	C(403)—C(402)—C(407)—H(25)	178.9
O(101)—C(101)—C(102)—H(2)	178.7	C(402)—C(403)—C(404)—H(22)	−178.0
O(101)—C(101)—C(102)—H(3)	−61.0	H(21)—C(403)—C(404)—C(405)	−179.1
C(103)—C(101)—C(102)—H(1)	−176.6	H(21)—C(403)—C(404)—H(22)	3.5
C(103)—C(101)—C(102)—H(2)	−56.8	C(403)—C(404)—C(405)—H(23)	178.9
C(103)—C(101)—C(102)—H(3)	63.6	H(22)—C(404)—C(405)—C(406)	179.7
C(104)—C(101)—C(102)—H(1)	−51.8	H(22)—C(404)—C(405)—H(23)	−3.7
C(104)—C(101)—C(102)—H(2)	68.0	C(404)—C(405)—C(406)—H(24)	179.0
C(104)—C(101)—C(102)—H(3)	−171.6	H(23)—C(405)—C(406)—C(407)	−178.9
O(101)—C(101)—C(103)—H(4)	−179.5	H(23)—C(405)—C(406)—H(24)	2.4
O(101)—C(101)—C(103)—H(5)	−58.4	C(405)—C(406)—C(407)—H(25)	−177.1
O(101)—C(101)—C(103)—H(6)	61.3	H(24)—C(406)—C(407)—C(402)	179.2
C(102)—C(101)—C(103)—H(4)	58.3	H(24)—C(406)—C(407)—H(25)	1.5

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
N201—H10···O302^i	0.95	2.07	2.946 (6)	153

Symmetry code: (i) −x+1, y−1/2, −z.