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.
An Improved Synthesis of (-)-(1<i>R</i>,2<i>S</i>,3<i>R</i>,4<i>S</i>)-2-Benzyloxy-3- bornanol (12) on a Preparative Scale
作者:Heinz Herzog、Hans-Dieter Scharf
DOI:10.1055/s-1986-31783
日期:——
A method is described for the separation of (-)-(1R,2S,3R, 4S)-2-benzyloxy-3-bornanol 12 in preparative amounts in the form of its formate 17 from the accompanying diastereomers 13-15.
β-hydroxy-α-amino acids is described. Nucleophilic addition of enolates of tricyclic iminolactones 1a and 1b to aldehydes in the presence of 6 equiv of lithium chloride in THF at −78 °C leads to aldol adducts in good yield (63−86%) and high diastereoselectivity (up to >25:1 dr). Subsequently, hydrolysis of the aldol adducts under acidic conditions leads to the corresponding β-hydroxy-α-amino acids in good yields
Reduction by a Model of NAD(P)H. 32. Stereoselective Reduction of Camphoroquinone by a Chiral NAD(P)H Model
作者:Atsuyoshi Ohno、Takehiko Goto、Jun-ichi Nakai、Shinzaburo Oka
DOI:10.1246/bcsj.54.3478
日期:1981.11
(+)-, (−)-, and racemic camphoroquinones (CQ) were reduced by each of four NAD(P)H-models such as N-(α-methylbenzyl)-1-propyl-2,4-dimethyl-1,4-dihydronicotinamide (Me2PNPH) in the presence of magnesium ion in acetonitrile with a view to elucidating the intermolecular arrangement in the transition state for asymmetric reduction. Partial rate factors for each attacking mode were calculated. Electronegative
[2+3]-cycloadditions of enantiomerically pure oxazoline-N-oxides1:A short stereoselective synthesis of (+)-carbovir
作者:Thierry Berranger、Yves Langlois
DOI:10.1016/0040-4039(95)01060-u
日期:1995.7
A short stereoselective synthesis of the potent antiviral agent carbovir 1 has been achieved by using a new [2+3] asymmetric cycloaddition between oxazoline-N-oxide 3 and cyclopentadiene.