Highly diastereoselective asymmetric syn-aldol reactions of (R)-(N-tosyl) phenylalaninol propionate-derived titanium enolate and bidentate aromatic and aliphatic aldehydes

Asymmetric aldol reactions of ester-derived titanium enolates of (R)-(N-tosyl)phenylalaninol propionate and bidentate aromatic aldehydes has been investigated. Substrate scope of this aldol reaction was examined with a variety of bidentate aromatic aldehydes to provide syn-aldol products with high diastereoselectivity and isolated yields. Both enantiomers of N-(tosyl)phenylalaninol are readily prepared from commercially available and optically active phenylalaninol. Mild saponification removed the chiral auxiliary and furnished optically active 8-hydroxy carboxylic acids.

Automated summary

The asymmetric aldol reactions between ester-derived chiral auxiliary and bidentate aromatic aldehydes have been investigated, leading to the synthesis of syn-aldol products with high diastereoselectivity and isolated yields. The enantiomers of optically active hydroxy carboxylic acids were obtained through the mild saponification of the chiral auxiliary.