PREMATURE REMOVAL OF N-ALPHA-9-FLUORENYLMETHYLOXYCARBONYL IN THERMODYNAMICALLY CONTROLLED ENZYMATIC COUPLING TRIALS

Incubation of N-proportional to-Fmoc-ISDR-OH and amino components in m ixtures of imethylformamide/1,1,1,3,3,3-hexafluoroisopropanol (DMF/HFI P), DMF/2,2,2-trifluoroethanol (TFE) or DMF/1,4-butanediol (BD), 0.2M Tris/HCl buffer, triethylamine (TEA) and trypsin, apparent pH range 8. 0-8.9, led to the undesired formation of variable amounts of dibenzofu lvene in the reaction media. Such side reaction, which resulted from a premature Fmoc removal, is minimised by the use 1M buffer or by the i ncrement of the trifluoroethanol proportion in the mixtures. (C) 1998 Published by Elsevier Science Ltd. All rights reserved.