cf. W., et al., CA 55, 13345h. The decompn. of such betaines derived from a nonmesomery-stabilized phosphorylide into their components was demonstrated in 2 ways. The betaine, Ph3+PCHMeCHPhO(I, erythro and threo forms) suspended in C6H6 or dissolved in Me3COH-Et2O treated with p-C1C6H4CHO and shaken 16 h. at 20 Deg yielded 38 and 52% cis- and trans-p-C1C6H4CH:CHMe together with 25 and 18% cis- and trans-PhCH:CHMe (from C6H6 and Me3COH-Et2O solns., resp.). I (90:10 or 99:1 threo-erythro) shaken 30 h. in C6H6 suspension at 20 Deg gave 50% I contg. 95:5 threo-erythro. Under the same conditions after 30 h. I contg. 10:90 threo-erythro had the compn. 75:25 threo-erythro. The diastereomeric relations were detd. by treating I with HBr in Et2O, isolating the mixt. of threo and erythro hydroxyphosphonium salts, (II), [Ph3P+CMeCHOHPh]-Br, and fractionating the salt from CH2Cl2 into the 94% erythro-rich component, m. 185-7 Deg, and the 80% threo-rich oil. Treatment of these fractions gave cis- and trans-MeCH:CHPh. The enriched II were converted with PhLi into the corresponding I. [on SciFinder (R)]