SYNTHESIS OF A C-14',C-15' DIHYDRO DERIVATIVE OF THE SOUTH HEXACYCLICSTEROID UNIT OF CEPHALOSTATIN-1 .1. REGIOSPECIFIC RH[II]-MEDIATED INTERMOLECULAR OXYGEN ALKYLATION OF A PRIMARY NEOPENTYL ALCOHOL
S. Bhandaru et Pl. Fuchs, SYNTHESIS OF A C-14',C-15' DIHYDRO DERIVATIVE OF THE SOUTH HEXACYCLICSTEROID UNIT OF CEPHALOSTATIN-1 .1. REGIOSPECIFIC RH[II]-MEDIATED INTERMOLECULAR OXYGEN ALKYLATION OF A PRIMARY NEOPENTYL ALCOHOL, Tetrahedron letters, 36(46), 1995, pp. 8347-8350
Hecogenin acetate 5 was converted to an intermediate suitable for the
construction of a C-14',C-15' dihydro derivative of the ''South'' hexa
cyclic spiroketal of cephalostatin 11. The key transformations include
: (i) proximal functionalization of the C-18 methyl group in 17 via hy
poiodite homolysis; (ii) Rhodium [II] catalyzed intermolecular oxygen
alkylation of primary neopentyl hydroxyl group in 20 and (iii) intramo
lecular Wadsworth-Emmons reaction to provide 23, the ester precursor o
f aldehyde 4.