Abstract
| - The total synthesis of the Annonaceous acetogenin (+)-asimicinis described. The approach employsthe (R)-α-OSEM allylic stannane 7 of >95% eeand the dialdehyde 8 obtained from(S,S)-diethyltartrate. Addition of 7 to 8 in the presenceof InCl3 afforded the bis-adduct 9 in 71%yield.Tosylation and treatment with TBAF led to the corebis-tetrahydrofuran intermediate, diol 11, in78% yield. Mono tosylation (n-BuLi, TsCl, THF−DMSO)and subsequent hydrogenolysis withLiBEt3H gave alcohol 14. The iodide15 was coupled with the higher-order vinylcyanocupratetoafford olefin 30. This was converted to diol31 of high ee by the Sharpless protocol. Thisdiolyielded the epoxide 33 via the mono-trisylate 32.Addition of (R)-lithio-2-(OTBS)-3-butyne inthepresence of BF3·OEt2 afforded the alcohol34. The SEM derivative 35 was treated withTBAF,and the resulting alcohol was converted to the butenolide 38by a sequence involving treatmentwith (CF3CO)2O, thenPd(PPh3)4, CO, THF−H2O, andfinally AgNO3/silica gel. Cleavage of theSEM protecting group with PPTS in ethanol afforded (+)-asimicin(39).
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