| abstract |
Methods are provided for preparing a compound with a fused ring structure of the formula (XIV), which comprises one or more reactions starting from a 21-cyano compound of the formula (XVI), wherein typically: R1 is a amidomethylene group or an acyloxymethylene group; R6 and R8 are independently selected from -H, -OH, or -OCOCH2OH, or R5 and R8 are both keto and ring A is a p-benzoquinone ring; R16a and R16b both are -H, oxone is -H and the other is -OH, -OCH2, or -OCH2CH3, or R14a and R14b together form a keto group; and R15 and R22 are independently selected from -H or -OH, or R5 and R6 are both keto and 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. |