US Patent 7241892 Hemisynthetic method and new compounds

Methods are provided for preparing a compound with a fused ring structure of formula (XIV) which comprises one or more reactions starting from a 21-cyano compound of formula (XVI) where typically: R1 is an amidomethylene group or an acyloxymethylene group; R5 and R8 are independently chosen from —H, —OH or —OCOCH2OH, or R5 and R8 are both keto and the ring A is a p-benzoquinone ring; R14a and R14b are both —H ozone is —H and the other is —OH, —OCH3 or —OCH2CH3, or R14a and R14b together form a keto group; and R15 and R18 are independently chosen from —H or —OH, or R5 and R8 are both keto and the ring A is a p-benzoquinone ring. In modified starting materials, the 21-cyano group can be replaced by other groups introduced using nucleophilic reagents.