Silyl Group Migration in 1-O-Silyl Protected Sugars-Convenient Synthesis of 2-O-Unprotected Sugars
摘要:
Reaction of 2-O-unprotected 1-O-silyl-protected D-glucose and D-galactose derivatives 5a-d with benzyl bromide in the presence of sodium hydride as the base afforded 1-O-benzyl 2-O-silyl derivatives 6a alpha/beta - 6d alpha/beta. Thus, prior to anomeric O-benzylation, trans-1,2-silyl group migration takes place. Ensuing removal of the 2-O-silyl group furnishes 2-O-unprotected compounds 8a alpha/beta - 8d alpha/beta, which are useful building blocks. More prone to 1-O-silyl group migration is mannose as shown for derivatives of 4,6-O-benzylidene-D-mannose 9. Cis-1,2- and cis-2,3-silyl group migrations affording compounds 15 and 13 were already observed on deacetylation of the thexyldimethylsilyl 2,3-di-O-acetyl derivative 12 beta under Zemplen conditions.
Ceric ammonium nitrate/acetic anhydride: A tunable system for the <i>O</i>-acetylation and mononitration of diversely protected carbohydrates
作者:Mohindra Seepersaud、Savita Seecharan、Lorale J. Lalgee、Nigel Kevin Jalsa
DOI:10.1080/00397911.2016.1230219
日期:2017.5.3
ABSTRACT Esterification of a wide range of partially protected carbohydrate derivatives was achieved using acetic anhydride and a catalytic amount of cericammoniumnitrate (CAN). Compatibility with the commonly used protecting groups was demonstrated, with the esterified products being furnished in good yields. Apart from affording the O-acetylated products, their mononitrated counterparts were also
摘要 使用乙酸酐和催化量的硝酸铈铵 (CAN) 实现了多种部分保护的碳水化合物衍生物的酯化。证明了与常用保护基团的相容性,酯化产物以良好的产率提供。除了提供 O-乙酰化产物外,还产生了它们的单硝化对应物,这取决于起始材料的反应性。降低 CAN 的摩尔当量只能提供 O-乙酰化产物,而增加它有利于单硝化衍生物。图形概要
Organocatalysis for the Acid-Free<i>O</i>-Arylidenation of Carbohydrates
作者:Yiqun Geng、Hassan M. Faidallah、Hassan A. Albar、Ibrahim A. Mhkalid、Richard R. Schmidt
DOI:10.1002/ejoc.201301116
日期:2013.11
p-methoxybenzaldehyde dimethyl acetal (3) and with benzaldehyde dimethyl acetal (7) as reagents in the presence of thiourea 1 or squaramide 2 as the organocatalyst to afford regioselectively 4,6-O-arylidenated derivatives 5 and 8. With an excess amount of 3 or 7, diarylidenated derivatives are also obtained. In situ formation of acetals of type 3 and 7 from corresponding aldehydes 10 and 13 in the presence
The present invention provides a compound of a formula (I):
or a pharmaceutically acceptable salt thereof; a process for preparing such a compound; and to the use of such a compound in the treatment of an ENaC mediated disease state (such as asthma, CF or COPD).
A unique approach to the synthesis of a dengue vaccine and the novel tetrasaccharide that results
作者:Nigel Kevin Jalsa、Gurdial Singh
DOI:10.1016/j.tetasy.2009.02.024
日期:2009.5
An approach to the development of a dengue vaccine by synthesizing the hexasaccharide epitope on the viral surface is examined. The stereochemical and structural challenges include the synthesis of a beta-mannoside bond. Synthesis of this bond is approached via a trisaccharide analogue portion of the epitope. A novel tetrasaccharide with a mannose-mannose anomeric linkage results in the Course of the synthetic attempts. (C) 2009 Elsevier Ltd. All rights reserved.
Patroni, Joseph J.; Stick, Robert V.; Skelton, Brian W., Australian Journal of Chemistry, 1988, vol. 41, # 1, p. 91 - 102
作者:Patroni, Joseph J.、Stick, Robert V.、Skelton, Brian W.、White, Allan H.