6 (-)パンクタチンAの全合成(口頭発表の部)

抄録

Total syntheses of the levorotatory enantiomer of punctatin A (antibiotic M95464) and the dextrorotatory enantiomer of punctatin D (antibiotic M167906) have been achieved. The identities of the synthetic materials with the corresponding natural products, which were confirmed spectroscopically and by [α]_D, permitted the assignment of absolute configuration. These structurally novel trans fused tertiary alcohol antibiotics were constructed in 16-19 steps from optically pure (99.6% ee) dextrorotatory diketone 5. Central to the synthetic strategy was (i) utilization of the Still rearrangement as a viable means for elaborating an angular hydroxymethylated cis-perhydroindan system and (ii) construction of the completely functionalized four-membered ring in proper stereochemical disposition by application of Norrish type II photochemistry. The conformational bias shown by selected intermediates and certain of their stereoisomers will be also discussed.