Combinatorial approach to flavor analysis. 1. Preparation and characterization of a S-methyl thioester library

A new method for the "one-pot" synthesis of S-methyl thioesters has been de veloped by reacting methyl chlorothiolformate with carboxylic acids. The re sulting "flavor library" contained all the intended thioesters and a single major impurity, identified by GC-MS as S,S-dimethyldithiocarbonate. Quanti fication of individual compounds present in the library was performed by GC analysis using two independent methods of detection, SCD and FID. It was s hown that apart from S-methyl thioacetate (0.8 mol %), molar concentrations of other thioesters varied in a relatively narrow range from 4.2 mol % for S-methyl thiopropionate to 14.1 mol % for S-methyl thiohexanoate. In gener al, medium chain S-methyl thioesters were present in slightly higher molar concentration's than those prepared from short or long chain carboxylic aci ds. This variation was attributed to partial loss of the most volatile comp onents during extraction and the lower reactivity of higher homologues. The library was used for the characterization of some physicochemical paramete rs of thioesters. In particular, lipophilicity coefficients (log k(w)) and thioester retention in 10, 20, and 33% triolein (used as a model lipid phas e) were determined directly by reverse-phase RPLC and extrapolated from the respective data. This analysis illustrates that substantial information ca n be generated using a library containing a relatively large number of comp ounds in effectively the same way as is necessary for the analysis of a sin gle sample.