1960 年 80 巻 9 号 p. 1193-1198
(-)-Menthyl and (+)-bornyl pyruvates, and (-)-menthyl and (+)-bornyl phenylglyoxylates were reacted respectively with ethynyllithium or 2-phenylethynyllithium, followed by reduction and hydrolysis to form atrolactic acid homologs. The optical rotations of these four products were compared with those of the same atrolactic acid homologs obtained by reaction of the foregoing four keto esters with ethyl- or phenethyl-magnesium bromide. The levorotatory compound was fractionated from dl-2-ethynyl-2-phenylglycolic acid and its reduction afforded (-)-2-ethyl-2-phenylglycolic acid. This starting acid and the product were proved to have the same configuration. The foregoing four keto esters were reacted with ethynyllithium and hydrolyzed without reduction. The optical rotations of the atrolactic acid homologs with a triple bond so obtained were compared with those of the products obtained as above and ethynyllithium was found to have the same reaction orientation properties against the carbonyl as alkylmagnesium bromide.
By the use of the present method, the hydroxyl group in 3-position of cyclolaudenol was directly proved to be the L-series as had been assumed to date and it was also proved by the present series of work that ethynyllithium can be used for determination of absolute configuration by the Prelog method.