S. Stankovic et al., STUDY OF LACTONIZATION PROCESS IN DEOXYCHOLIC-ACID ANALOGS BY MODELING - STRUCTURE OF -ACETOXY-24-NOR-5-BETA-CHOLANO-12-ALPHA,24-LACTONE, Zeitschrift fur Kristallographie, 213(3), 1998, pp. 151-154
The title compound was synthesized from 3 alpha-acetoxy-1 2 alpha-hydr
oxy-24-nor-5 beta-cholan-23-oic acid by treating it with dichloroethyl
phosphate and triethylamine. The crystals are orthorhombic, space grou
p P2(1)2(1)2(1), a = 19.166(2) Angstrom, b = 14.109(2) Angstrom, c = 8
.246(1) Angstrom, V = 2229.9(6) Angstrom(3), Z = 4, D-c = 1.189 g cm(-
3) lambda(CuKalpha) = 1.5418 Angstrom, mu = 0.55 mm(-1), F(000) = 880,
T = 298 K. The structure was solved by direct methods and refined to
R = 0.049 for 894 observed reflections collected on a CAD-4 diffractom
eter. The molecules in the crystal are in their monolactone form. Ener
gy calculations, based on molecular modeling were carried out for simi
lar molecules containing 6- to 11-membered monolactone and 12- to 22-m
embered bislactone rings. The relative minimum energy values, obtained
by MMX calculations, show a considerable decrease for monolactone rin
gs with less than eight members, and a considerable increase for the b
islactones with less than sixteen atoms. The MMX calculations are in a
greement with current experimental results which indicate that the mon
olactonization occurs only in cases where the number of atoms forming
the lactone ring is less than eight.