Synthetic angucyclines, 3. First total synthesis ofrac-rabelomycin by Diels-Alder reaction

✍ Scribed by Krohn, Karsten ;Khanbabaee, Karamali ;Flörke, Ulrich ;Jones, Peter G. ;Chrapkowski, Axel

• Publisher: John Wiley and Sons
• Year: 1994
• Tongue: English
• Weight: 775 KB
• Volume: 1994
• Category: Article
• ISSN: 0947-3440
• DOI: 10.1002/jlac.15619940505

✦ Synopsis

Abstract

Conjugate addition of the 2‐siloxydienes 5a and 5b to juglone (4a) or 3‐chlorojuglone (4b) affords the products 6–8a and 8b, respectively. The reaction of 4a with furan 10 yields the substitution product 11, which is converted to the 5‐hydroxybutenolide 12 by treatment with MCPBA. Hexamethyldisilane (13) is cleaved by treatment with methyllithium to afford lithium pentamethyldisilane (14), which adds to enone 15 in a Michael reaction to give the adduct 16. The diene 18 is constructed regioselectively from 16 by a Wittig‐Horner reaction and silylation. The Diels‐Alder reaction of 18 with juglone (4a) affords adducts 19a and 19b, which are converted to racemic rabelomycin (2) by hydroxylation and photooxygenation. The structures of four products (8a, 8b, 9, 12) were confirmed by X‐ray structure determination. magnified image