Enzyme as resolving agents

Enzymes are also used as resolving agents because of their ability to catalyze a reaction of one enantiomer but not that of its mirror image. 

Efficient kinetic resolution of chiral unsaturated secondary alcohols by irreversible enzyme-mediated acylation (with vinyl acetate as acylating agent, a crude preparation of Pseudomonas AK, and hexane as solvent) is possible, provided one relatively large and one small substituent are attached to the carbinol carbon. However, the method can be used to resolve substrates that are not amenable to asymmetric epoxidation (see examples 23, 25, 27, 29, where the double bond is either deactivated by an electron-withdrawing substituent, or is of the propargyl alcohol type). Acylation of the / -enantiomer consistently proceeds faster than that of the 5-enantiomer. An example of an allenic alcohol was also reported248. 

A number of 1- and 2-aminophosphonates were resolved by a straight CAL-B-promoted acetylation of the amino group in the substrates rac-SS. Surprisingly, ethyl acetate had to be used as an acetylating agent, since the commonly applied vinyl acetate reacted with aminoalkanephosphonates even in the absence of an enzyme (Equation 30, Table 6). ... 

Delavirdine (Rescriptor) is approved for the treatment of HIV-1 infection in adults and adolescents over age 16 as part of a combination therapy. Rash accompanied by pruritus is the most frequent adverse effect of this agent however, it usually resolves within several weeks of treatment. Severe skin reactions are rare. Headache, nausea, vomiting, diarrhea, fatigue, and elevated hepatic enzymes also may be associated with delavirdine administration. 

We have found that mixing polyacrylamide and starch expands the versatility of both. In our experience, many enzymes that are not well resolved on starch or acrylamide alone are well-resolved on a mixture of the two. The five acrylamide/starch concentrations (weight/volume) we use most often are (1) 12% starch, (2) 7% acrylamide, (3) 9% acrylamide, (4) 7% acrylamide with 2% starch, and (5) 6% acrylamide with 4% starch. For gels containing acrylamide, the total amount of gelling agent is prepared as 95% acrylamide and 5% iV.iV -methylenebisacrylamide. Gel polymerization catalysts, ammonium persulfate (APS) and N,N,N, N -tetxa.-methylethylenediamine (TEMED), are 0.1% (w/v) and 0.2% (v/v) of the total volume of the gel buffer, respectively. 

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