Prelog-Djerassi lactone. Preparation of the grieco intermediate from (−)-trans-pulegenic acid.

✍ Scribed by Salih Hacini; Maurice Santelli

• Publisher: Elsevier Science
• Year: 1989
• Tongue: French
• Weight: 392 KB
• Volume: 45
• Category: Article
• ISSN: 0040-4020
• DOI: 10.1016/s0040-4020(01)89521-1

✦ Synopsis

The Grieco intermediate 2, for the synthesis of the Prelog-Djerassi lactone, was obtained from trans-pulegenic acid 3 in 6 steps in 43 9b overall yield; recycling unwanted diastereoisomer SCS_I, increased the yield to 56 %. The Prelog-Djerassi lactone 1 is a key degradation product of the antibiotics methymycin (1) and narbomycin (2), which retains the original four chiral centers present in the C(l)-C(7)(1) or C(3)-C(9)(2) fragments of the aglycons (3). Since the first synthesis by Masamune in 1975 (41, several studies have been devoted to the preparation of 1 because of its potential utility in the contruction of complex natural products (5X6). Our own strategy is centered on the levorotatory Grieco intermediate 2 (7)(8), which comes from the (-)_%-pulegenic acid 3 derived from the (g)-(-)-pulegone 4. The latter is easily prepared from various sources in high optical purity (9).