Steroidal Analogue of Deoxyvernolepin. Synthesis of d-Lactone Key Intermediate

Sesquiterpene lactones of elemanolide type vernolepin 1 and deoxyvernolepin 2 exhibit a pronounced antitumor activity against the Walker intramuscular carcinosarcoma 256 and CCRF - CEM human lymphoblastic leukemia cells in culture and were therefore, subjects of many partial and total syntheses. The synthesis of the steroidal analogue of deoxyvernolepin 3, i. e., its key interrnediate, d-lactone 28-hydroxy-2-oxa-5a,10a- cholest-6-en-3-one 4 starting from cholesterol is the subject of this report. Known reactions, as well as modified ones, were used in the synthesis. A new reaction for the preparation of dimethyl acetals with pyridinium chlorochromate and methanol was also developed. It was found that the acetalization reaction using pyridinium chlorochromate and methanol could be performed without affecting an acid-sensitive functional groups such as the oxirane ring