N. Harada, Masataka Watanabe, S. Kuwahara
Apr 7, 2000
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Tetrahedron-asymmetry
Abstract
Abstract Racemic 2-methoxy-2-(1-naphthyl)propionic acid ( 1 , MαNP acid) was enantioresolved as its esters derived from various chiral alcohols. For example, a diastereomeric mixture of esters prepared from (±)- 1 and (1 R ,3 R ,4 S )-(−)-menthol was easily separated by HPLC on silica gel yielding esters (−)- 2a and (−)- 2b , the separation factor α=1.83 being unusually large. The 1 H NMR chemical shift differences, Δδ=δ( R )–δ( S ), between diastereomers 2a and 2b , are much larger than those of conventional chiral auxiliaries, e.g. Mosher’s MTPA and Trost’s MPA acids. This acid 1 is therefore very powerful for determining the absolute configuration of chiral alcohols by the 1 H NMR anisotropy method. Solvolysis of the separated esters yielded enantiopure acids ( S )-(+)- 1 and ( R )-(−)- 1 , which are useful for enantioresolution of racemic alcohols.