Synthesis of natural ecteinascidins (ET-729, ET-745, ET-759B, ET-736, ET-637, ET-594) from cyanosafracin B.

The semisynthetic process initially described for the synthesis of 1 (ET-743) has been extended to the preparation of other natural ecteinascidins. For the synthesis of 2 (ET-729) a demethylation of a N-Me intermediate was carried out by a selective oxidation with MCPBA. Other natural ecteinascidins (ET-745, ET-759B, ET-736, ET-637, ET-594) were accessible from key intermediate 25. The described methodologies allow for the preparation of a wide variety of ecteinascidins by procedures that can be easily scaled up.