Protection Chloromethyl ethyl ether

Protection of ethyl L-lactate with a BOM group is readily accomplished with chloromethyl benzyl ether in the presence of Hunig s base [100,101]. 

The ribavirin analogues 36 and 37 were prepared by the conversion of ethyl cyanoformate 31 to ethyl carboethoxyformimidate 32, whose reaction with formylhydrazine gave 33, which then thermally cyclized to 34. Coupling this synthon with the protected chiral chloromethyl ethers of 1,3-di-O-benzylbutane-l,2/ ,35-triol and l,3,4-tri-0-benzylbutane-l,2R,3S,4-tetrol 26 gave 35. The ester function was converted to the carboxamide moiety, and the side-chain was deprotected to give the T,2 -5eco-nucleosides 36 and 37 (88JHC651). 

Ethyl lactate can be protected as a BOM ether for subsequent nucleophilic additions to the corresponding aldehyde with high diastereoselectivity. A synthesis of zoapatanol used selective protection of a diol (eq 3). Primary alcohols can be protected selectively in the presence of secondary hydroxy groups, and secondary hydronyls react more quickly than tertiary ones with benzyl chloromethyl ether and base. Removal of this protecting group can be carried out by hydrogenolysis over Pd. 

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