Concise asymmetric routes to 2,2,4-trisubstituted tetrahydrofurans via chiral titanium imide enolates: Key intermediates towards synthesis of highly active azole antifungals SCH 51048 and SCH 56592
作者:Anil K Saksena、Viyyoor M Girijavallabhan、Haiyan Wang、Yi-Tsung Liu、Russel E Pike、Ashit K Ganguly
DOI:10.1016/0040-4039(96)01203-8
日期:1996.8
approaches to the key (−)-(2R)-cis-tosylate 1 and its (+)-(2S)-enantiomer 15 via generation of chiralimideenolates having a 2,2-disubstituted olefin functionality in the β-position, are described. In a “protecting group free” sequence, reaction of the titanium enolate generated from (4R)-benzyl-2-oxazolidinone derived imide 5b with s-trioxane provided a convenient intermediate 19 which could be directly
Highly stereoselective access to novel 2,2,4-substituted tetrahydrofurans by halocyclization: Practical chemoenzymatic synthesis of Sch 51048, a broad-spectrum orally active antifungal agent
作者:Anil K Saksena、Viyyoor M Girijavallabhan、Raymond G Lovey、Russell E Pike、Haiyan Wang、Ashit K Ganguly、Brian Morgan、Alexsey Zaks、Mohinder S Puar
DOI:10.1016/0040-4039(95)00143-z
日期:1995.3
A convenient synthesis of (−)-(2R)-cis-tosylate 2 is reported via stereoselective 5-exo iodocyclization of the optically active 2,2-disubstituted olefin 9a. Enzymatic desymmetrization of the homoallylic diol 4 with Novo SP435 allowed optimal pro-(S) selectivity to provide the desired (−)-(S)-monoacetate 9a. Under the irreversible reaction conditions, the presence of a bulky aryl substituent on the