X-RAY STRUCTURE OF (SP)-L-MENTHYL (2-METHOXYPHENYL)PHENYLPHOSPHINYL-ACETATE AND ASSIGNMENT OF CONFIGURATION IN MENTHYL PHOSPHINYLACETATES

The structure and absolute configuration of enantiomeric (S(P))-L-ment hyl 2(methoxy-phenyl)phenylphosphinylacetate, the only crystalline of the two P-epimers, was analyzed by a single-crystal X-ray diffraction technique. C25H33O4P, space group P2(1)2(1)2(1), a = 9.890(1)angstrom. b = 10.011(3)angstrom, c = 24.177(3)angstrom, V = 2393.7(8)angstrom3, Z = 4. The structure was solved by direct methods and was refined by full matrix least-squares calculations to R = 0.045 using 2697 unique reflections with I > 3sigma(I). The absolute configuration was determi ned by the Hamilton method. The P=O and C=O dipoles of the studied mol ecule were found oriented in a syn fashion and the phenyl and the meth oxyphenyl rings were both arranged coplanarly with the P=O bond. Two i ntermolecular C-H ... 0 short contacts involving methoxyphenyl hydroge ns and P=O and C=O oxygens were revealed. A potential possibility of u sing differentiated crystallinity of P-epimeric menthyl phosphinylacet ates as a mnemonic for the assignment of their configuration at P is d iscussed.