Effective protection of the N-sulfate of glucosamine derivatives with the 2,2,2-trichloroethyl group
摘要:
The 2,2,2-trichloroethyl (TCE) group was utilized as the first protecting group for N-sulfates (chlorosulfuric acid TCE ester, Et3N, DMAP, DMF). Glycosylation with 3,4,6-tri-O-acetyl-N-trichloroethylsulfuryl-alpha-D-glucosaminosyl trichloroacetimidate provided the corresponding beta-glucosaminosides stereoselectively and in excellent yields. The TCE protection stayed stable under a variety of conditions for the manipulation of other protecting groups, and was readily removable with zinc in the presence of ammonium chloride in methanol. (c) 2008 Elsevier Ltd. All rights reserved.
Effective protection of the N-sulfate of glucosamine derivatives with the 2,2,2-trichloroethyl group
摘要:
The 2,2,2-trichloroethyl (TCE) group was utilized as the first protecting group for N-sulfates (chlorosulfuric acid TCE ester, Et3N, DMAP, DMF). Glycosylation with 3,4,6-tri-O-acetyl-N-trichloroethylsulfuryl-alpha-D-glucosaminosyl trichloroacetimidate provided the corresponding beta-glucosaminosides stereoselectively and in excellent yields. The TCE protection stayed stable under a variety of conditions for the manipulation of other protecting groups, and was readily removable with zinc in the presence of ammonium chloride in methanol. (c) 2008 Elsevier Ltd. All rights reserved.
Rh-catalyzed alkene oxidation: a highly efficient and selective process for preparing N-alkoxysulfonyl aziridines
作者:Kiran Guthikonda、Paul M. Wehn、Brian J. Caliando、J. Du Bois
DOI:10.1016/j.tet.2006.07.099
日期:2006.12
Unique alkoxysulfonyl aziridine heterocycles were prepared through selective intra- and intermolecular alkeneoxidation reactions. These methods are general and perform efficiently at low Rh-catalyst loadings (1–2 mol %) with only a slight excess of an inexpensive commercial oxidant, PhI(OAc)2. For intermolecular processes, trichloroethylsulfamate was identified as a novel and markedly effective N-atom
A regio- and stereo-controlled, one-pot amidoglycosylation of alcohols has been achieved using O-acetylated glycals, trichloroethoxysulfonamide, and iodosobenzene in the presence of a rhodium(ii) catalyst.
of alcohols has been developed using O-acetylated glycals, trichloroethoxysulfonamide, and iodosobenzene. This one-pot amidoglycosylation was applied to a variety of primary and secondaryalcohols to afford the beta-O-glycosides with acceptable yields up to 84%. The reaction would proceed via stereoselective intermolecular aziridination of the glycal from the alpha-face followed by SN2 reaction with
<i>O</i>- and <i>N</i>-Sulfations of Carbohydrates Using Sulfuryl Imidazolium Salts
作者:Laura J. Ingram、Ahmed Desoky、Ahmed M. Ali、Scott D. Taylor
DOI:10.1021/jo9014112
日期:2009.9.4
A series of sulfuryl imidazolium salts (SISs) were prepared and examined as reagents for incorporating trichloroethyl-protected sulfate esters into carbohydrates. The SIS that contained a 1,2-dimethylimidazolium moiety (SIS 9) proved to be a superior sulfating compared to SISs bearing no alkyl groups or bulkier alkyl groups on the imidazolium ring. Difficult O-sulfations that required prolonged reaction times and a large excess of the SIS bearing a 1-methylimidazolium group (SIS 5) were achieved in high yield using less than half the amount of SIS 9 in less time. Certain N-sulfated compounds that were practically inaccessible using SIS 5 were obtained in excellent yield using SIS 9.