The total synthesis of (-)-tetrahydrolipstatin utilizing two approaches is described. In the first, L-malic acid was used as a chiral template to obtain enantiomerically pure (R)-3-(benzyloxy)-tetradecanal (11) which was chain-extended using 1-(trimethylsilyl)-2-nonene and a Lewis acid. This advanced intermediate was further elaborated to the target compound in good overall yield. The second approach utilized lauraldehyde as a starting material and capitalizes on an asymmetric allylboronation (91 % ee). The product could be obtained enantiomerically pure by conversion to the (R)-acetoxymandelate ester and hydrolysis. Oxidative cleavage of the terminal double bond led to 11 which was further extended using 1,3- and 1,2-asymmetric induction based on existing neighboring chirality. The synthesis of tetrahydrolipstatin using the second approach comprises seven steps from 11 and proceeds in 38 % overall yield.
Oxazoline <i>N</i>-Oxide-Mediated [2+3] Cycloadditions. Application to a Synthesis of (−)-Tetrahydrolipstatin
作者:O. Dirat、C. Kouklovsky、Yves Langlois
DOI:10.1021/ol990734k
日期:1999.9.1
[reaction: see text] A [2+3] cycloaddition of camphor-derived oxazolineN-oxide to alpha,beta-unsaturated ester afforded adduct 8. Tetrahydrolipstatin 1 was prepared from this compound in a nine-step sequence of reactions.