Monitoring the solid-phase synthesis of depsides and depsipeptides. A color test for hydroxyl groups linked to a resin.

A color test for the detection of hydroxyl groups bonded to a solid support and useful for the control of solid-phase synthesis of depsides and depsip eptides is described. It is carried out directly on the resin and shows a v iolet to pink color with primary, secondary and tertiary alcohols, and phen ols. 16 mu mol of free OH groups per g of resin can be easily detected with the naked eye using this procedure. The reaction is based on the formation of the tosylate, its displacement with p-nitrobenzylpyridine and conversio n of the resin-bound pyridinium salt to a strongly colored internal salt by treatment with base. Amino and carboxyl groups are negative in these condi tions. Full loading of Wang and Merrifield resins can be efficiently checke d using this test. (C) 1999 Elsevier Science Ltd. All rights reserved.