First Synthesis of 12‐Oxosoladulcidine and Its Derivatives as Potential Antitumor Steroidal Alkaloids

The first synthesis of 12‐oxosoladulcidine (=(3 β ,5 α ,22 α ,25 R )‐3‐hydroxyspirosolan‐12‐one; 4 ) is reported, and its structure was confirmed by single‐crystal X‐ray diffraction analysis. Compound 4 was readily obtained in five steps in an overall yield of 31%, starting from hecogenin ( 5 ). By slightly modifying the synthetic protocol, eight analogues of 4 were also prepared. The title compound and its derivatives are expected to be potent antitumor alkaloids, since structurally closely related to the known antitumor agents soladulcidine ( 2 ) and hecogenin ( 5 ).