Direct glycosylation of protected O-tritylserine esters and oligopeptides
摘要:
N-Finoc-3-O-Tr-L-serine methyl and benzyl esters, as well as a tripeptide FmocAlaSeI(Tr)GlyOBn were directly glycosylated by 3,4,6-tri-O-acetyl-1,2-O-(1-cyanoethylidene)-alpha-D-galactopyranose in the presence of TrClO(4) in dichloromethane, yielding 32-57% of N-Fmoc-3-O-(2,3,4,6-tetra-O-acetyl-beta-D-galactopyranosyl)-L-serine esters and the corresponding tripeptide.
We report the visible light photocatalytic cleavage of trityl thioethers or ethers under pH-neutral conditions. The method results in the formation of the respective symmetrical disulfides and alcohols in moderate to excellent yield. The protocol only requires the addition of a suitable photocatalyst and light rendering it orthogonal to several functionalities, including acid labile protective groups
A highly efficient In(III) triflate-assisted method for the detritylation of O-trityl derivatives of carbohydrates, phenols, and alcohols using solvent-free mechanochemical method is described. In the case of carbohydrates, further reaction in the presence of an acceptor sugar leads to highly efficient glycosylation in the same pot resulting in the formation of the desired glycoside-product in very high yields. The method was applied successfully to the synthesis of a combinatorial library of galactose-based (1,6)-linked cyclo-hexa-, hepta-, and octasaccharides on gram scale. (C) 2014 Elsevier Ltd. All rights reserved.