Synthesis of optically pure (+)-puraquinonic acid and assignment of absolute configuration to natural (-)-puraquinonic acid. Use of radical cyclization for asymmetric generation of a quaternary center.
An asymmetric aldol reaction between aldehyde 31 and imide 32, followed at a later stage by ring-closing metathesis (38 --> 40), are key reactions used to make optically pure allylic alcohol 40. Radical cyclization of the derived Stork bromo acetals gives lactol ethers 43, which were degraded to generate a quaternary center carrying a methoxycarboxyl group (44 --> 47). Compound 47 was converted into (+)-puraquinonic acid; and comparison with a natural sample established that the configuration of the natural compound is 2R (1).
Clive
Derrick L J
DL
Chemistry Department, University of Alberta, Edmonton, Alberta, Canada T6G 2G2. derrick. clive@ualberta.ca
Yu
Maolin
M
Sannigrahi
Mousumi
M
D000970:Antineoplastic Agents / Q000138:chemical synthesis / Q000737:chemistry; D002454:Cell Differentiation; D003500:Cyclization; D006801:Humans; D007192:Indenes / Q000138:chemical synthesis* / Q000737:chemistry; D013237:Stereoisomerism
D000970:Antineoplastic Agents; D007192:Indenes; C431681:puraquinonic acid