New methods for elucidating the absolute configuration of Type A alcohol and Type B carboxylic acid are reported. Determination of the absolute configurations of such kind of long-chain compounds has been extremely difficult and they have usually remained undetermined. Optically active 2NMA (2-naphthylmethoxyacetic acid; 1) was obtained in gram scale by chromatographic separation of the diastereomers C and D followed by acid hydrolysis. The absolute configurations of the long-chain alcohols 3, 4, 5, and 6 have been determined by analyzing the NMR spectra of their esters of (R) and (S)-1. In all the cases, the protons located on the same plane with the 2-naphthyl groups of 1 greatly shifted upfield, which made the assignment very easy. Magnitude of Δδ values gave hints about the conformation of the respective compounds. PGDA (phenylglycine dimethyl amide; 7) and PGME (phenylglycine methyl ester; 8) have been developed as the chiral anisotropic reagents for elucidation of the carboxylic acid of Type B. The conformation of the amides, B-PGDA and B-PGME, was assumed as H by consideration of the electronic repulsion of the substituents. Eventually the conformation H was verified by X-ray analysis of 9, MM calculation on 11, and NOE study on 10. PGDA and PGME were applied to the carboxylic acids 11-17, the absolute configurations of which are known. Δδ values (Δδ=δ_R-δ_S; see model B) are depicted in each structure. The absolute configurations derived from the present method are in all cases the same as known ones,. which means that the method using PGDA and PGME is applicable to the carboxylic acid whose absolute configuration is unknown.
