Higher water-soluble substrates

Epoxidation Oxone alone (1.5-2 equiv.) can effect epoxidation of alkenes. Yields are generally higher if the pH is maintained at 6 by addition of KOH. Water-soluble substrates (sorbic acid) are epoxidized in water aqueous methanol is used for water-insoluble substrates. 

Lipases (triacylglycerol acyl hydrolases, EC 3.1.1.3), have been well established as a valuable catalyst in organic synthesis.12 They are usually distinguished from carboxyl esterases (EC 3.1.1.1) by their substrate spectra, i.e. esterases prefer water soluble substrates and lipases show significantly higher activity towards their natural substrates,... 

When applied to carbohydrates, the sono-allylation proceeded with useful diastereoselectivity (rAreo-selectivity) and allowed preparation of higher-carbon sugars from water-soluble substrates directly in aqueous ethanol without protection (Schmid and Whitesides, 1991). Later, the authors showed that the allylation of aldoses could be advantageously carried out by heating the reaction mixture for example, the allylation of D-arabinose required 16-20h under sonication, but only 2h under reflux (Kim et al., 1993) ... 

Higher homologues of glycine have also been evaluated as pro-moieties of active alcohols or phenols. Thus, the highly lipophilic a-tocopherol was de-rivatized with a series of m-aminoalkanecarboxylic acids in the search for a water-soluble, injectable provitamin E [146], Good to high water solubility was indeed achieved. The esters were substrates of liver esterases and showed marked structure-dependent differences in their rate of enzymatic hydrolysis. 

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