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Solid-phase synthesis of peptidyl thioacids employing a 9-fluorenylmethyl thioester-based linker in conjunction with Boc chemistry.

A method for the synthesis of peptidyl thioacids is described on the basis of the use of the N-[9-(thiomethyl)-9H-fluoren-2-yl]succinamic acid and cross-linked aminomethyl polystyrene resin. The method employs standard Boc chemistry SPPS techniques in conjunction with 9-fluorenylmethyloxycarbonyl protection of side-chain alcohols and amines and 9-fluorenylmethyl protection of side-chain acids and thiols. Cleavage from the resin is accomplished with piperidine, which also serves to remove the side-chain protection and avoids the HF conditions usually associated with the resin cleavage stage of Boc chemistry SPPS. The so-obtained thioacids are converted to simple thioesters in high yield by standard alkylation according to well-established methods.