respect to modifications at the c 20 position the isoprenyl group at the c 20 position can be ozonized to yield a ketone 15 at c 20 position as set forth in equation l a variety of reactions performed on the ketone functionality can provide a series of different derivatives for example the ketone functionality of compound 15 can be easily converted to a variety of oximes furthermore a number of additional oxime derivatives 16 can be prepared through substitution reactions at the hydroxyl group of the hydroxyloxime with electrophiles as set forth in equation m str11 wherein r k h or c 1 c 16 alkyl or r k coc 6 h 4 x or r k coch 2 y or r k ch 2 chch 2 or ch 2 ccr 1 the ketone functionality also can undergo a reductive amination reaction with a series of aliphatic and aromatic amines in the presence of nabh 3 cn to provide a corresponding substituted amine 17 at the c 20 position as set forth in equation n str12 wherein r l c 1 c 16 alkyl or r l c 6 h 4 x or r l coc 6 h 4 x or r l coch 2 y or r l ch 2 chch 2 or ch 2 ccr 1 the ketone can be reacted with a series of lithium acetylides to.