PHOTOLABILE MULTI‐DETACHABLE p‐ALKOXYBENZYL ALCOHOL RESIN SUPPORTS FOR PEPTIDE FRAGMENT OR SEMI‐SYNTHESIS

Abstract
Two photolabile multi‐detachable alkoxybenzyl alcohol resins, 2‐[4‐(oxymethyl)phenoxy]propionyl‐resin 4 and 4‐[4‐(oxymethyl)phenoxymethyl]‐3‐nitrobenzamidomethyl‐resin 5 have been synthesized. Bpoc‐peptide attached to resin 4 or 5 when treated with 50% trifluoroacetic acid provided the free, unprotected peptide, but on photolysis gave Bpoc‐peptide p‐hydroxybenzyl ester. Removal of the p‐hydroxybenzyl ester in aqueous base or by oxidative work up gave a protected Bpoc‐peptide suitable for fragment synthesis at its C‐terminus. However, methylation of the ester to Bpoc‐peptide p‐methoxybenzyl ester followed by removal of the Bpoc‐group gave a protected peptide p‐methoxybenzyl ester suitable for fragment coupling at its N‐terminus. The efficacies of these resins were evaluated in the syntheses of a model tetrapeptide and an octapeptide by using NαBpoc‐, Fmoc‐ and Nps‐amino acids. The use of 2‐thiopyridine with pyridinium hydrochloride as a new and efficient thiolytic reagent for the deprotection of the Nps‐group was studied.

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