Synthesis of Enantiopure Aliphatic Acetylene Alcohols and Determination of Their Absolute Configurations by 1 H NMR Anisotropy and/or X‐ray Crystallography

The MαNP acid method has been applied to racemic aliphatic acetylene alcohols in order to simultaneously prepare enantiopure alcohols and to determine their absolute configurations by 1 H NMR anisotropy. Racemic acetylene alcohols 6 – 8 , 11 , and 20 were esterified with MαNP acid ( S )‐(+)‐ 1 to yield diastereomeric MαNP esters which were efficiently separated by HPLC on silica gel with separation factors α in the range 1.60–1.93. The 1 H NMR anisotropy factors Δ δ [= δ (2nd fr.) – δ (1st fr.)] were calculated from the data of the first‐ ( 22a – 27a ) and second‐eluted MαNP esters ( 22b – 27b ). The absolute configurations of the first‐eluted esters were determined from the distribution of Δ δ values in the MαNP sector rule. In the case of MαNP ester 26b , the assigned absolute configuration was confirmed by X‐ray crystallography. The solvolysis of MαNP esters yielded enantiopure acetylene alcohols 5 – 8 with established absolute configurations. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)