Journal of the American Chemical Society, Vol.121, No.10, 2071-2084, 1999
Cephalostatin synthesis. 15. Synthesis of the South unit of cephalostatin. 7. Total syntheses of (+)-cephalostatin 7, (+)-cephalostatin 12, and (+)-ritterazine K
Transformation of alcohol 4 to alpha-azidoketone 6, a hexacyclic steroid bearing the requisite functionality and spiroketal stereochemistry of the symchiral South portion of cephalostatin 7 (10) is described. Reaction of a 1:1 mixture of alpha-azidoketones 5 and 6 with sodium hydrogen telluride is followed by cleavage of the protecting groups cephalostatin 12 (9), cephalostatin 7 (10), and ritterazine K (11).