1018907-22-6Relevant articles and documents
Stereochemistry of cycloaddition of (S)-N-(1-phenylethyl)-C-diethoxyphosphorylated nitrone with vinyl acetate. Studies on mutarotation of 3-(O,O-diethylphosphoryl)-5-hydroxyisoxazolidines
Piotrowska, Dorota G.
, p. 279 - 287 (2008)
Three enantiomerically pure diethyl 5-acetoxy-2-[(S)-1-phenylethyl]isoxazolidinyl-3-phosphonates were obtained by 1,3-dipolar cycloaddition of the title nitrone and vinyl acetate. Each of them was subsequently transformed into the respective 5-hydroxy derivatives, which exist as equilibrium mixtures of C5-anomers. Detailed mutarotation studies on a 3-(O,O-diethylphosphoryl)-5-hydroxyisoxazolidine system showed that trans-isomer (3S,5R) is favoured in the solid state, whereas after 48 h in chloroform-d solution it epimerises at C5 to an (89:11) equilibrium mixture of (3S,5S)- and (3S,5R)-isomer. The major (3S,5S)-anomer adopts a single E3 conformation, which is stabilised by the C3-P(O)...HO-C5 hydrogen bond. Absolute configurations of the cycloadducts were established based on conformational analysis employing 1H, 13C and 31P NMR data and confirmed by the transformation of the (3S,5R)-isomer into the known (S)-(+)-phosphohomoserine.
