Abstract Modified Mosher's method has been extended by use of 9-anthranylmethoxyacetic acid (9ATMA) and 2-naphthylmethoxynaphthylacetic acid (2NMA) instead of MTPA of the conventional method. Anisotropic effects of these reagents are much greater than that of MTPA, and the reagents have been shown to be useful especially to determine the absolute configurations of the secondary alcohols involved in long-chain compounds.