Synthesis of d-xylopyranan by the ring-opening polymerization of 3-O-benzyl-α-d-xylopyranose 1,2,4-orthopivalate. Attempts to synthesize a stereoregular polymer
摘要:
3-O-Benzpl-alpha -D-xylopyranose 1,2,4-orthopivalate (1) was newly synthesized and polymerized under cationic polymerization reaction conditions in order to synthesize stereoregular (1 --> 4)-beta -D-xylopyranan. Although the polymerization of orthopivalate 1 was carried out under various reaction conditions, a non-stereoregular polymer, but mainly consisting of (1 --> 4)-beta -xylopyranose units, was obtained. Comparing these results with those of glucose 1,2,4-orthopivalates, it was revealed that not only the substituents in the C-2 and C-3 positions, but also the CH2OR group in glucose 1,2,4-orthopivalate, largely contribute to (1 --> 4)-beta -glucosidic bond formation by the ring-opening polymerization. (C) Published by Elsevier Science Ltd.
Stereoselektive Glycosylierung von Steroidalkoholen mit 2,3,4,6-Tetra-O-privaloyl-α-D-glucopyranosylbromid (Pivalobromglucose) und 2,3,4,6-Tetra-O-(o-toluoyl)-α-D-glucopyranosylbromid
作者:Albrecht Harreus、Horst Kunz
DOI:10.1002/jlac.198619860411
日期:1986.4.15
elektronischen und sterischen Gründen in ihrer Reaktivität differieren und die darüber hinaus empfindliche Gruppierungen enthalten, werden mit 2,3,4,6-Tetra-O-pivaloyl-α-D-glucopyranosylbromid (1) selektiv und effektiv in β-Glucoside übergeführt. Dank des lenkenden Einflusses des 2-O-Pivaloyl-Substituenten wird eine Orthoesterbildung bei den Koenigs-Knorr-Reaktionen stark unterdrückt. Mit dem o-Toluoylrest
各种结构的甾醇,其羟基官能团由于电子和空间原因而具有不同的反应性,并且还包含敏感基团,它们对2,3,4,6 - tetra - O - pivaloyl -α-D-具有选择性并有效吡喃葡萄糖基溴化物(1)转化为β-葡萄糖苷。由于2- O-新戊酰基取代基的直接影响,在Koenigs-Knorr反应中原酸酯的形成被强烈抑制。用邻甲苯甲酰基作为羟基保护基,这种控制只能在很小的程度上实现。
Organoboron-Promoted Regioselective Glycosylations in the Synthesis of a Saponin-Derived Pentasaccharide from <i>Spergularia ramosa</i>
作者:Ross S. Mancini、Corey A. McClary、Stefi Anthonipillai、Mark S. Taylor
DOI:10.1021/acs.joc.5b00950
日期:2015.9.4
Organoboron-mediated regioselective glycosylations were employed as key steps in the total synthesis of a branched pentasaccharide from a saponin natural product. The ability to use organoboron activation to differentiate OH groups in an unprotected glycosyl acceptor, followed by substrate-controlled reactions of the obtained disaccharide, enabled a streamlining of the synthesis relative to a protective group-based approach. This study revealed a matching/mismatching effect of the relative configuration of donor and acceptor on the efficiency of a regioselective glycosylation reaction, a problem that was solved through the development of a novel boronic acid-amine copromoter system for glycosyl acceptor activation.