[GRAPHICS]The direct formation Of beta-L-rhamnopyranosides by means of thioglycoside donors protected with a 2-O-sulfonate ester and, ideally, a 4-O-benzoyl ester, is reported. Activation is achieved with the combination of 1-benzenesulfinyl piperidine and triflic anhydride in the presence of 2,4,6-tri-tert-butylpyrimidine. Selectivities vary from moderate to good, and the sulfonyl group is easily removed post-glycosylation with sodium amalgam in 2-propanol.
It is shown that the use of 5% acetonitrile or propionitrile in dichloromethane functions to increase the beta-selectivity of a number of L-rhamnopyranosylation reactions conducted by the thioglycoside method with activation by the 1-benzenesulfinyl piperidine/trifluoromethanesulfonic anhydride couple. The use of more significant quantities of acetonitrile or propionitrile results in the formation of complex reaction mixtures containing little coupled product, but from which Ritter-type products can be isolated. (c) 2006 Elsevier Ltd. All rights reserved.
Direct Synthesis of the β-<scp>l</scp>-Rhamnopyranosides
作者:David Crich、John Picione
DOI:10.1021/ol0340890
日期:2003.3.1
[GRAPHICS]The direct formation Of beta-L-rhamnopyranosides by means of thioglycoside donors protected with a 2-O-sulfonate ester and, ideally, a 4-O-benzoyl ester, is reported. Activation is achieved with the combination of 1-benzenesulfinyl piperidine and triflic anhydride in the presence of 2,4,6-tri-tert-butylpyrimidine. Selectivities vary from moderate to good, and the sulfonyl group is easily removed post-glycosylation with sodium amalgam in 2-propanol.
On the nitrile effect in l-rhamnopyranosylation
作者:David Crich、Mitesh Patel
DOI:10.1016/j.carres.2006.03.036
日期:2006.7
It is shown that the use of 5% acetonitrile or propionitrile in dichloromethane functions to increase the beta-selectivity of a number of L-rhamnopyranosylation reactions conducted by the thioglycoside method with activation by the 1-benzenesulfinyl piperidine/trifluoromethanesulfonic anhydride couple. The use of more significant quantities of acetonitrile or propionitrile results in the formation of complex reaction mixtures containing little coupled product, but from which Ritter-type products can be isolated. (c) 2006 Elsevier Ltd. All rights reserved.