Di-O-Alkylated Tartrates

A significent portion of this chapter has been devoted to protection of the vicinal dihydroxy functionalities of tartaric acid derivatives with various cyclic protecting groups that may or may not participate in synthesis of the desired product. However, many noncyclic protecting groups are also available. Of these, the dialkylated derivatives will be discussed first. 

Disparlure, [cw-(7i ,85)-( + )-7,8-epoxy-2-methyloctadecane] (490) is the sex pheromone of the female gypsy moth Prothetria dispar L. Its stereoselective synthesis utilizes the threo configuration present in diethyl (2i ,3i )-( + )-tartate (lb). Conversion of 577, prepared 

A variant of the Williamson reaction for the preparation of ethers utilizes thallium ethoxide to convert the vicinal hydroxy groups in tartaric esters to the thallium(I) oxide derivative 590, which upon treatment with alkyl halides provides excellent yields of dialkylated tartaric esters 569 [189]. 

Conversion of lb to the dimethylamide 591 [190] and introduction of thallium ethoxide followed by treatment with an appropriate alkyl halide generates in good to excellent yield the di-O-alkylated tartaramides 592 [189]. 

592c R = n-Ci6H33 (95%) 592d R = n-Ci8H37(84%) 592e R = CH2Ph(89%) 

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