N-Phthaloyl-L-alanyl-L-phenyl­alanine methyl ester

The title compound, C₂₁H₂₀N₂O₅, is a terminally protected dipeptide. The backbone adopts an extended conformation, with the phthaloyl group orthogonal to the plane of the trans peptide link. The phenyl­alanine side chain adopts the g^- conformation. In the crystal lattice, the mol­ecules are stacked with a strong intermolecular hydrogen bond between the H atom of the amide link and the amide carbonyl group of a neighbour.

Key indicators

• Single-crystal X-ray study
• T = 149 K
• Mean [sigma](C-C) = 0.005 Å
• R factor = 0.038
• wR factor = 0.086
• Data-to-parameter ratio = 6.9

checkCIF results

No syntax errors found

ADDSYM reports no extra symmetry


 Alert Level C:



ABSMU_01  Alert C The ratio of given/expected absorption coefficient lies
          outside the range 0.99 <> 1.01
          Calculated value of mu =     0.096
          Value of mu given      =     0.100

REFNR_01  Alert C Ratio of reflections to parameters is < 8 for a
          non-centrosymmetric structure, where ZMAX < 18
          sine(theta)/lambda                0.5879
          Proportion of unique data used    1.0000
          Ratio reflections to parameters   6.9216

THETM_01  Alert C The value of sine(theta_max)/wavelength is less than 0.590
          Calculated sin(theta_max)/wavelength =    0.5879

General Notes



REFLT_03
         From the CIF: _diffrn_reflns_theta_max           24.70
         From the CIF: _reflns_number_total               1765
         Count of symmetry unique reflns         1822
         Completeness (_total/calc)             96.87%
         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.


 0 Alert Level A = Potentially serious problem

 0 Alert Level B = Potential problem

 3 Alert Level C = Please check

---

Computing details

Data collection: XSCANS (Bruker, 1997); cell refinement: XSCANS; data reduction: SHELXTL (Siemens, 1994); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997) and TITAN2000 (Hunter & Simpson, 1999); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997) and TITAN2000; molecular graphics: ORTEP-3 (Farrugia, 1997); software used to prepare material for publication: SHELXL97.

(I)

Crystal data

C21H20N2O5	F(000) = 400
Mr = 380.39	Dx = 1.335 Mg m^−3
Monoclinic, P21	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: P 2yb	Cell parameters from 3956 reflections
a = 10.9627 (5) Å	θ = 1.1–24.7°
b = 4.8481 (2) Å	µ = 0.10 mm^−1
c = 18.5150 (9) Å	T = 149 K
β = 105.991 (1)°	Needle, colourless
V = 945.96 (7) Å^3	0.65 × 0.10 × 0.05 mm
Z = 2

Data collection

Bruker CCD area-detector diffractometer	1635 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.055
Graphite monochromator	θmax = 24.7°, θmin = 1.1°
φ and ω scans	h = −11→12
3956 measured reflections	k = −5→2
1765 independent reflections	l = −21→20

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)] = 0.038	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.086	H-atom parameters constrained
S = 1.13	w = 1/[σ^2(Fo^2) + (0.0271P)^2 + 0.4579P] where P = (Fo^2 + 2Fc^2)/3
1765 reflections	(Δ/σ)max < 0.001
255 parameters	Δρmax = 0.20 e Å^−3
1 restraint	Δρmin = −0.22 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. 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.

As no heavy atom is present in the molecule, the absolute structure could not be determined reliably and the corresponding Flack parameter is not quoted.

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

	x	y	z	Uiso*/Ueq
C1	0.2459 (3)	0.3336 (7)	0.10294 (16)	0.0221 (7)
O1	0.17048 (18)	0.4884 (5)	0.11886 (12)	0.0304 (6)
C2	0.2278 (3)	0.1365 (6)	0.03985 (16)	0.0210 (7)
C3	0.1225 (3)	0.0794 (8)	−0.01960 (17)	0.0274 (7)
H3	0.0444	0.1732	−0.0253	0.033*
C4	0.1359 (3)	−0.1215 (8)	−0.07076 (17)	0.0323 (8)
H4	0.0652	−0.1661	−0.1119	0.039*
C5	0.2499 (3)	−0.2576 (8)	−0.06309 (18)	0.0328 (8)
H5	0.2565	−0.3921	−0.0992	0.039*
C6	0.3554 (3)	−0.1987 (8)	−0.00273 (17)	0.0273 (7)
H6	0.4338	−0.2922	0.0033	0.033*
C7	0.3419 (3)	−0.0009 (7)	0.04758 (15)	0.0208 (6)
C8	0.4360 (3)	0.1047 (7)	0.11638 (16)	0.0210 (7)
O2	0.54493 (18)	0.0296 (5)	0.14180 (11)	0.0270 (5)
N1	0.3736 (2)	0.3100 (6)	0.14528 (12)	0.0194 (5)
C9	0.4182 (3)	0.4643 (7)	0.21531 (15)	0.0202 (6)
H9	0.3788	0.6520	0.2076	0.024*
C10	0.5629 (3)	0.4985 (8)	0.24190 (17)	0.0285 (7)
H10A	0.6025	0.3188	0.2572	0.043*
H10B	0.5852	0.6257	0.2847	0.043*
H10C	0.5933	0.5730	0.2008	0.043*
C11	0.3726 (3)	0.3160 (7)	0.27663 (16)	0.0190 (6)
O3	0.3670 (2)	0.0643 (5)	0.27885 (12)	0.0260 (5)
N2	0.3461 (2)	0.4841 (6)	0.32773 (12)	0.0195 (5)
H2	0.3488	0.6638	0.3217	0.023*
C12	0.3130 (3)	0.3747 (6)	0.39291 (15)	0.0185 (7)
H12	0.3695	0.2122	0.4106	0.022*
C13	0.1757 (3)	0.2679 (7)	0.37526 (16)	0.0232 (7)
H13A	0.1636	0.1243	0.3359	0.028*
H13B	0.1637	0.1790	0.4210	0.028*
C14	0.0743 (3)	0.4846 (7)	0.34919 (16)	0.0238 (7)
C15	0.0422 (3)	0.5847 (8)	0.27603 (18)	0.0309 (8)
H15	0.0865	0.5189	0.2420	0.037*
C16	−0.0530 (3)	0.7785 (9)	0.2518 (2)	0.0401 (9)
H16	−0.0722	0.8470	0.2019	0.048*
C17	−0.1204 (3)	0.8728 (9)	0.3003 (2)	0.0442 (10)
H17	−0.1865	1.0042	0.2838	0.053*
C18	−0.0898 (3)	0.7728 (10)	0.3730 (2)	0.0435 (10)
H18	−0.1352	0.8364	0.4066	0.052*
C19	0.0057 (3)	0.5820 (8)	0.39710 (19)	0.0331 (8)
H19	0.0253	0.5155	0.4473	0.040*
C20	0.3488 (2)	0.5891 (7)	0.45466 (16)	0.0194 (7)
O4	0.41779 (19)	0.7816 (5)	0.45439 (11)	0.0265 (5)
O5	0.29751 (18)	0.5332 (5)	0.51066 (11)	0.0303 (6)
C21	0.3345 (3)	0.7155 (10)	0.57493 (18)	0.0416 (10)
H21A	0.4172	0.6581	0.6074	0.062*
H21B	0.2710	0.7069	0.6032	0.062*
H21C	0.3404	0.9049	0.5577	0.062*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
C1	0.0214 (15)	0.0227 (18)	0.0225 (16)	0.0006 (14)	0.0069 (12)	0.0013 (14)
O1	0.0236 (11)	0.0342 (14)	0.0322 (12)	0.0070 (12)	0.0057 (9)	−0.0059 (11)
C2	0.0242 (15)	0.0221 (18)	0.0185 (15)	−0.0013 (14)	0.0086 (12)	0.0010 (13)
C3	0.0208 (14)	0.0335 (19)	0.0270 (17)	−0.0002 (15)	0.0050 (12)	−0.0019 (16)
C4	0.0335 (18)	0.041 (2)	0.0219 (17)	−0.0088 (17)	0.0060 (13)	−0.0071 (16)
C5	0.0351 (18)	0.036 (2)	0.0292 (18)	−0.0077 (17)	0.0127 (14)	−0.0109 (16)
C6	0.0286 (16)	0.0277 (18)	0.0287 (17)	0.0007 (16)	0.0131 (13)	−0.0014 (16)
C7	0.0242 (15)	0.0227 (16)	0.0174 (14)	−0.0015 (14)	0.0088 (11)	0.0012 (14)
C8	0.0249 (16)	0.0224 (17)	0.0171 (15)	−0.0009 (14)	0.0084 (12)	0.0049 (13)
O2	0.0227 (11)	0.0307 (14)	0.0272 (11)	0.0052 (10)	0.0061 (8)	0.0028 (11)
N1	0.0194 (12)	0.0220 (14)	0.0164 (12)	0.0004 (12)	0.0044 (9)	0.0013 (11)
C9	0.0247 (15)	0.0182 (16)	0.0164 (14)	0.0010 (13)	0.0037 (12)	0.0011 (13)
C10	0.0276 (16)	0.0301 (18)	0.0260 (17)	−0.0068 (16)	0.0045 (13)	−0.0010 (16)
C11	0.0195 (15)	0.0170 (18)	0.0181 (15)	−0.0004 (14)	0.0012 (12)	0.0009 (13)
O3	0.0404 (13)	0.0148 (13)	0.0238 (11)	−0.0003 (10)	0.0108 (9)	−0.0001 (9)
N2	0.0279 (13)	0.0114 (12)	0.0195 (12)	−0.0001 (11)	0.0068 (10)	0.0010 (11)
C12	0.0227 (15)	0.0167 (16)	0.0166 (15)	0.0016 (13)	0.0061 (11)	0.0009 (12)
C13	0.0277 (16)	0.0199 (17)	0.0209 (15)	−0.0037 (15)	0.0049 (12)	−0.0037 (14)
C14	0.0206 (14)	0.0218 (16)	0.0256 (16)	−0.0044 (14)	0.0007 (12)	−0.0056 (14)
C15	0.0271 (16)	0.034 (2)	0.0282 (18)	0.0005 (17)	0.0023 (13)	−0.0047 (16)
C16	0.0351 (18)	0.041 (2)	0.0369 (19)	0.0028 (19)	−0.0019 (15)	0.0034 (19)
C17	0.0245 (17)	0.042 (2)	0.060 (3)	0.0084 (17)	0.0010 (16)	−0.004 (2)
C18	0.0329 (19)	0.052 (3)	0.047 (2)	0.007 (2)	0.0139 (16)	−0.008 (2)
C19	0.0285 (16)	0.038 (2)	0.0336 (18)	0.0005 (17)	0.0101 (14)	−0.0034 (17)
C20	0.0167 (14)	0.0191 (16)	0.0207 (15)	0.0035 (14)	0.0024 (12)	0.0022 (13)
O4	0.0335 (12)	0.0211 (12)	0.0228 (11)	−0.0054 (11)	0.0041 (9)	0.0011 (10)
O5	0.0287 (11)	0.0435 (16)	0.0211 (11)	−0.0116 (12)	0.0106 (9)	−0.0115 (12)
C21	0.043 (2)	0.056 (3)	0.0290 (19)	−0.016 (2)	0.0153 (16)	−0.0195 (19)

Geometric parameters (Å, º)

C1—O1	1.212 (4)	N2—C12	1.453 (3)
C1—N1	1.408 (4)	N2—H2	0.8800
C1—C2	1.480 (4)	C12—C20	1.514 (4)
C2—C3	1.386 (4)	C12—C13	1.540 (4)
C2—C7	1.389 (4)	C12—H12	1.0000
C3—C4	1.394 (5)	C13—C14	1.509 (4)
C3—H3	0.9500	C13—H13A	0.9900
C4—C5	1.385 (5)	C13—H13B	0.9900
C4—H4	0.9500	C14—C15	1.390 (5)
C5—C6	1.399 (4)	C14—C19	1.394 (4)
C5—H5	0.9500	C15—C16	1.384 (5)
C6—C7	1.373 (4)	C15—H15	0.9500
C6—H6	0.9500	C16—C17	1.389 (5)
C7—C8	1.492 (4)	C16—H16	0.9500
C8—O2	1.212 (3)	C17—C18	1.382 (5)
C8—N1	1.395 (4)	C17—H17	0.9500
N1—C9	1.460 (4)	C18—C19	1.377 (5)
C9—C10	1.535 (4)	C18—H18	0.9500
C9—C11	1.539 (4)	C19—H19	0.9500
C9—H9	1.0000	C20—O4	1.202 (4)
C10—H10A	0.9800	C20—O5	1.336 (3)
C10—H10B	0.9800	O5—C21	1.448 (4)
C10—H10C	0.9800	C21—H21A	0.9800
C11—O3	1.223 (4)	C21—H21B	0.9800
C11—N2	1.339 (4)	C21—H21C	0.9800
O1—C1—N1	123.7 (3)	C11—N2—H2	119.4
O1—C1—C2	129.8 (3)	C12—N2—H2	119.4
N1—C1—C2	106.5 (2)	N2—C12—C20	107.8 (2)
C3—C2—C7	121.0 (3)	N2—C12—C13	113.6 (2)
C3—C2—C1	131.1 (3)	C20—C12—C13	115.2 (2)
C7—C2—C1	107.9 (2)	N2—C12—H12	106.6
C2—C3—C4	117.3 (3)	C20—C12—H12	106.6
C2—C3—H3	121.4	C13—C12—H12	106.6
C4—C3—H3	121.4	C14—C13—C12	115.1 (3)
C5—C4—C3	121.6 (3)	C14—C13—H13A	108.5
C5—C4—H4	119.2	C12—C13—H13A	108.5
C3—C4—H4	119.2	C14—C13—H13B	108.5
C4—C5—C6	120.6 (3)	C12—C13—H13B	108.5
C4—C5—H5	119.7	H13A—C13—H13B	107.5
C6—C5—H5	119.7	C15—C14—C19	117.8 (3)
C7—C6—C5	117.7 (3)	C15—C14—C13	121.4 (3)
C7—C6—H6	121.2	C19—C14—C13	120.7 (3)
C5—C6—H6	121.2	C16—C15—C14	121.3 (3)
C6—C7—C2	121.8 (3)	C16—C15—H15	119.4
C6—C7—C8	129.8 (3)	C14—C15—H15	119.4
C2—C7—C8	108.4 (3)	C15—C16—C17	120.1 (3)
O2—C8—N1	126.8 (3)	C15—C16—H16	119.9
O2—C8—C7	127.2 (3)	C17—C16—H16	119.9
N1—C8—C7	106.0 (2)	C18—C17—C16	119.0 (4)
C8—N1—C1	111.2 (2)	C18—C17—H17	120.5
C8—N1—C9	128.8 (2)	C16—C17—H17	120.5
C1—N1—C9	119.4 (2)	C19—C18—C17	120.7 (3)
N1—C9—C10	113.8 (2)	C19—C18—H18	119.6
N1—C9—C11	108.6 (3)	C17—C18—H18	119.6
C10—C9—C11	109.3 (2)	C18—C19—C14	121.1 (3)
N1—C9—H9	108.3	C18—C19—H19	119.4
C10—C9—H9	108.3	C14—C19—H19	119.4
C11—C9—H9	108.3	O4—C20—O5	124.1 (3)
C9—C10—H10A	109.5	O4—C20—C12	124.2 (3)
C9—C10—H10B	109.5	O5—C20—C12	111.7 (3)
H10A—C10—H10B	109.5	C20—O5—C21	115.6 (3)
C9—C10—H10C	109.5	O5—C21—H21A	109.5
H10A—C10—H10C	109.5	O5—C21—H21B	109.5
H10B—C10—H10C	109.5	H21A—C21—H21B	109.5
O3—C11—N2	124.1 (3)	O5—C21—H21C	109.5
O3—C11—C9	121.4 (3)	H21A—C21—H21C	109.5
N2—C11—C9	114.5 (3)	H21B—C21—H21C	109.5
C11—N2—C12	121.1 (3)
O1—C1—C2—C3	2.4 (6)	C8—N1—C9—C11	−93.3 (3)
N1—C1—C2—C3	−178.2 (3)	C1—N1—C9—C11	77.2 (3)
O1—C1—C2—C7	−177.8 (3)	N1—C9—C11—O3	36.0 (4)
N1—C1—C2—C7	1.6 (3)	C10—C9—C11—O3	−88.7 (4)
C7—C2—C3—C4	0.3 (5)	N1—C9—C11—N2	−146.9 (2)
C1—C2—C3—C4	180.0 (3)	C10—C9—C11—N2	88.4 (3)
C2—C3—C4—C5	−0.5 (5)	O3—C11—N2—C12	2.7 (4)
C3—C4—C5—C6	0.7 (6)	C9—C11—N2—C12	−174.4 (2)
C4—C5—C6—C7	−0.6 (5)	C11—N2—C12—C20	153.8 (2)
C5—C6—C7—C2	0.4 (5)	C11—N2—C12—C13	−77.4 (3)
C5—C6—C7—C8	−180.0 (3)	N2—C12—C13—C14	−64.4 (3)
C3—C2—C7—C6	−0.2 (5)	C20—C12—C13—C14	60.6 (3)
C1—C2—C7—C6	180.0 (3)	C12—C13—C14—C15	77.9 (4)
C3—C2—C7—C8	−179.9 (3)	C12—C13—C14—C19	−105.0 (3)
C1—C2—C7—C8	0.3 (3)	C19—C14—C15—C16	1.2 (5)
C6—C7—C8—O2	−1.1 (6)	C13—C14—C15—C16	178.4 (3)
C2—C7—C8—O2	178.5 (3)	C14—C15—C16—C17	−1.3 (6)
C6—C7—C8—N1	178.3 (3)	C15—C16—C17—C18	0.8 (6)
C2—C7—C8—N1	−2.0 (3)	C16—C17—C18—C19	−0.2 (6)
O2—C8—N1—C1	−177.5 (3)	C17—C18—C19—C14	0.1 (6)
C7—C8—N1—C1	3.1 (3)	C15—C14—C19—C18	−0.6 (5)
O2—C8—N1—C9	−6.3 (5)	C13—C14—C19—C18	−177.8 (3)
C7—C8—N1—C9	174.3 (3)	N2—C12—C20—O4	−15.5 (4)
O1—C1—N1—C8	176.5 (3)	C13—C12—C20—O4	−143.4 (3)
C2—C1—N1—C8	−3.0 (3)	N2—C12—C20—O5	166.5 (2)
O1—C1—N1—C9	4.3 (5)	C13—C12—C20—O5	38.6 (3)
C2—C1—N1—C9	−175.1 (3)	O4—C20—O5—C21	−2.6 (4)
C8—N1—C9—C10	28.6 (4)	C12—C20—O5—C21	175.4 (3)
C1—N1—C9—C10	−160.8 (3)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
N2—H2···O3^i	0.88	2.13	2.983 (3)	164

Symmetry code: (i) x, y+1, z.