Methyl group, latent

The key reaction in these syntheses was the stereoselective introduction of angular cyano groups as latent methyl groups into perhydropolycyclic a, (3-unsaturated compounds. The new hydrocyanation method developed gave excellent chemoselectivity and stereochemical control. 

A potentially attractive route to 0-roethylnucleosldes is based on the use of the [[2-(methylthio)phenyl]thio]methyl group for the protection of primary and secondary hydroxy functions.This protecting group is stable under both acidic and basic conditions and functions as a latent 0-methyl group. For example, 5 -0-[[[2-(methylthio)phenyl]thio]methyl]-2 -deoxythymldine (105) is readily converted into 5 -0-methylthymidine in 68Z yield by treatment with tributyltin hydride and azobls(isobutyronitrile). Alternatively, deprotection to give thymidine can be accomplished using mercury (II) chloride in aqueous acetonitrile. 

The cyclopropyl group serves not only as the latent angular methyl group but also allows direct methylation of the ketone for introduction of the gem dimethyl function. 

Esters. Most acryhc acid is used in the form of its methyl, ethyl, and butyl esters. Specialty monomeric esters with a hydroxyl, amino, or other functional group are used to provide adhesion, latent cross-linking capabihty, or different solubihty characteristics. The principal routes to esters are direct esterification with alcohols in the presence of a strong acid catalyst such as sulfuric acid, a soluble sulfonic acid, or sulfonic acid resins addition to alkylene oxides to give hydroxyalkyl acryhc esters and addition to the double bond of olefins in the presence of strong acid catalyst (19,20) to give ethyl or secondary alkyl acrylates. 

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