Search

In the title compounds, C(22)H(29)ClO(3), (I), and C(21)H(29)ClO(2), (II), respectively, the B rings adopt a half-chair conformation and the D rings adopt an envelope conformation. A twist of the steroid skeleton of both compounds is observed. There is a positional disorder of the acetoxy group of (II), with the terminal atoms disordered over two positions with near equal occupancy. Quantum-mechanical ab initio calculations using a molecular orbital Hartree-Fock method were performed for the isolated molecules, thus allowing the distinction within the structural features of these two androstane derivatives of which characteristics are intrinsic to the molecules and which are due to packing effects. The skeletal twisting was found to be innate to the molecules, while the acetoxy disorder is due to packing effects.

The structures of O-acetyl-N-(5-phenyl-2-pyridyl)-hydroxylamine, C 13 H 12 N 2 O 2 , (I), and O-acetyl-N-(2-pyridyl)hydroxylamine, C 7 H 8 N 2 O 2 , (II), have been determined in order to confirm earlier structure assignments based on spectroscopic information. Compound (I) is the probable mutagenic metabolite of the phenylalanine pyrolysis product 2-amino-5-phenylpyridine. The crystal structures of (I) and (II) are the first reported for heterocyclic N-acetoxyarylamines, the corresponding homocyclic arylamine derivatives being extremely unstable. In the solid state, both (I) and (II) exist as hydrogen-bonded dimers, with the arylamine N atom acting as donor and the pyridine N atom of a neighboring inversion-related molecule as acceptor; the distance between donor and acceptor N atoms is 3.007 (2) in (I) and 2.956(2) A in (II). This orientation of the N-H bond results in the rotation of the acetoxy group out of the plane of the pyridine ring by 22.5 (2) in (I) and 27.4 (2)° in (II).

The crystal structures of two intact limonoids, nimonol,7α-­acetyl-17α-(3-furyl)-6α-hydroxy-4α,4β,8β-trimethyl-5α,18α-androsta-1,14-dien-3-one (C28H36O5), and 6-oxonimonol,7α-acetyl-17α-(3-furyl)-4α,4β,8β-trimethyl-5α,18α-androsta-1,14-diene-3,6-dione (C28H34O5), are reported. The molecular features are mostly the same in the two structures; however the orientations of the acetoxy group are different in the two structures. The packing in nimonol is due to O—H⋯O hydrogen bonds while in 6-oxonimonol it is due to C—H⋯O hydrogen bonds.

The title compound, C 23 H 34 O 6 , a ring D lactone, has two acetoxy groups in positions 3α and 4β. All ring junctions are trans which results in a planar molecule. The two acetoxy groups have different behaviour, one of them being disordered and exhibiting double-bond delocalization. The ordered acetoxy group is involved in two weak intramolecular C-H… O bonds.

The title compound, C12H14O6, has been isolated from a Fries reaction on 3,6-dihydroxy-2,4-dimethoxyacetophenone. Its molecular structure contains an intramolecular hydrogen-bonded unit involving the –COCH3 and –OH substituents. The best plane through the acetoxy group makes a dihedral angle of 88.74 (5)° with the plane of the aromatic ring.

C23H25NO7.1⁄2C4HsO2, M r = 471.49, is o r t h o r h o m bic, P212121, with a = 9.299 (3), b = 10.534 (4), c = 27.084 (6) A, V = 2653 (4) A 3, z = 4, 2(Mo Ka) = 0.71069 A, D c = 1.180, D m -1.16 (2) Mg m -3. The structure was solved by the Patterson search approach where the molecular structure of isocolchicine was used as the search model and refined by full-matrix leastsquares methods. The final R value was 0.077 for 1552 observed reflections. The ethyl acetate molecule shows an occupation factor of 0.5, and the acetamido O atom is disordered. The position of the acetoxy group in the solid state defines the molecule as belonging to the isocolchicine series. The conformation of colchiceine acetate may explain its lack of accessibility at the tubulin binding site and therefore its decreased biological activity.

M~= 242183 ~ orthorhombic, P2~2~2~, a= 9.495 (2), = • (3), c= 5.841(1) A, V= 903.2 (3)/~a, Z=4, D x=l.575gcm -3, CuKa, 2 = 1.5418 A,/t = 11.4 cm -~, F(000) = 440, T= 293 K, R=0.036 (wR=0.053) for 999 reflections. The structure is of interest because the compound is a derivative of citric anhydride and consists of two fused five-membered rings, one of which is an anhydride and the other a y-lactone, with one carbon of the fusion bearing an acetoxy group. The molecule has bond lengths and angles comparable with those of other anhydrides. The packing is determined by interaction between carbonyl and ether oxygen atoms.

CsHI5N709, Mr=353.25 , orthorhombic, Pbca, a = 12.410 (2), b = 9.695 (1), c = 25.079 (3)A, V= 3017.5 (6) A 3, Z = 8, D x = 1.555 g em -3, 2(Cu Kct) = 1.54178 A, # = 11.9 cm -~, F(000) = 1472, T= 295 K, final R = 0.066, wR = 0.067 for 1427 independent reflections. The acetoxy group is disordered such that the two conformations for the group have occupancies of 57 and 43%. Bond distances and angles are normal and intermolecular hydrogen bonding occurs between the secondary amine and the nondisordered acetyl O atom. Experimental. A clear colorless 0.05 x 0.10 x 0.25 mm data crystal, crystallized from methyl chloride was provided by C. Coon of Lawrence Livermore Laboratory. Automated Nieolet R3m diffractometer