Syntheses of spacer-armed carbohydrate model compounds
摘要:
Commercially available chemicals, such as diethylene glycol, 1,9-nonanediol, 9-decen-1-ol, 1,2,6-hexanetriol, and p-nitrophenol were used to prepare spacer-armed carbohydrate derivatives. Glycosides of D-glucose, N-acetyl-D-glucosamine and 3-O-methyl-D-glucose have been synthesized, carrying reactive groups at the end of the spacer-arms. These glycosides are capable of forming neoglycoproteins. When bromo sugars were reacted with highly apolar aglycones in the presence of mercuric cyanide or mercuric bromide, a considerable amount of '2-OH-compounds' (such as 9-hydroxynonyl 3,4,6-tri-O-acetyl-beta-D-glucopyranoside) were formed. Some spacer-armed derivatives (such as 9,10-epoxydecyl beta-D-glucopyranoside) are theoretically a mixture of diastereomers, but this fact does not mirror in the H-1 and C-13 NMR spectra. (C) 1997 Elsevier Science Ltd.
Erbium(III) trifluoromethane sulfonate is proposed as a very gentle Lewis acid catalyst in a MW-assisted chemoselective method for the cleavage of isopropylideneacetals in awkward substrates by using pure water as the solvent.
of α-amino acids from the corresponding 1,2-diols has been developed. This process enables the directsynthesis of free α-amino acids without any protection/deprotection step. This method was also effective for the preparation of a 15N-labeled α-amino acid. 1,2-Diols bearing α,β-unsaturated ester moieties afforded bicyclic α-amino acids through intramolecular [3 + 2] cycloadditions. A preliminary study
Selective cleavage of acetals with ZnBr2 in dichloromethane
作者:Celia Ribes、Eva Falomir、Juan Murga
DOI:10.1016/j.tet.2005.10.064
日期:2006.2
A selective cleavage of acetals of 1,2- and 1,3-diols has been achieved under mild conditions using ZnBr2 in dichloromethane at room temperature. Acetal types cleavable by this procedure include benzylidene, isopropylidene and cyclohexylidene acetals. This method is compatible with several other types of hydroxyl protecting groups such as Bn, Bz, TBDPS, TIPS and TBDMS. (c) 2005 Published by Elsevier Ltd.