Study on the synthesis of brassinolide and related compounds III : Stereoselective synthesis of typhasterol from hyodeoxycholic acid

✍ Scribed by Wei-Shan Zhou; Wei-Sheng Tian

• Publisher: Elsevier Science
• Year: 1987
• Tongue: French
• Weight: 450 KB
• Volume: 43
• Category: Article
• ISSN: 0040-4020
• DOI: 10.1016/s0040-4020(01)86858-7

✦ Synopsis

Typhasterol 2 was synthesized stereoselectively from hyodeoxycholic acid 3. The aldehyde 5 derived from 3 was reacted with the anion of 3-methylbutenolide under kinetic condition to afford (22R,23R)-7 as the major product. Hydrogenation of 7 and its 22-acetate 14 over PtO2-Pt/C yielded the expected compound 8 and 15, respectively, in very good yield. Typhasterol was obtained from 8 and 15 through the following sequence of reaction 849-10 -+12+13--rZ and lS-r16--17-13-Z. Since the discovery of novel plant-growth hormone brassinolide 1 in 1979l, a number of new brassinosteroids in other higher plant have been isolated and 2 identified . A simple analogue of brassinolide isolated from cat-tail pollen (Typha latifolia L.) represents the first example of 2-deoxy-brassinosteroid plant-growth hormone3. Although synthesis of brassinolide and its analogues has been achieved by several research groups from stigmasterol or ergosterol as st-4 arting material , the synthesis of them starting from hyodeoxycholic acid 3 has not yet been reported. In our previous work, we have finished the conversion of A,B ring of hyodeoxycholic acid into the A,B ring of brassinolide' and the synthesis of a stereoisomer of typhasterol 2, (22S,23S)-4 from 36. We now wish to report here the synthesis of natural typhasterol 2 also starting from 3.