Stereocontrolled entry to β-C-glycosides and bis-C,C-glycosides from C-glycals: preparation of a highly functionalized triene from d-mannose
摘要:
The C(3) hydroxyl group of C-glycals can be readily converted into mixed halo-acetals of 2-bromo-acetaldehyde. Radical reaction of the latter mediated by tri-n-butyltin hydride, with or without a radical acceptor, led diastereoselectively to either beta -C-glycosides or bis-C,C-glycosides, respectively. The latter have been transformed into a highly functionalized triene, which is a potential precursor in a proposed synthesis of labdane type diterpenes from D-mannose. (C) 2001 Elsevier Science Ltd. All rights reserved.
This report describes the first example of palladium-catalyzed ortho-C–H glycosylation/ipso-alkenylation of aryliodides, and the easily accessible glycosyl chlorides are used as a glycosylation reagent. The reaction is compatible with the functional groups of the substrates, and a series of C-aryl glycosides have been synthesized in good to excellent yield and with excellent diastereoselectivity.
In this work, we describe a Catellani-type C-H glycosylation to provide rapid access to various highly decorated α-C-(hetero)aryl glycosides in a modular and stereoselective manner (>90 examples). The termination step is flexible, which is demonstrated by ipso-Heck reaction, hydrogenation, Suzuki coupling, and Sonogashira coupling. Application of this methodology has been showcased by preparing gl
Synthesis of glycosyl chlorides with acid-labile protecting groups
作者:Shang-Cheng Hung、Chi-Huey Wong
DOI:10.1016/0040-4039(96)01006-4
日期:1996.7
Glycosyl chlorides with acid-labileprotectinggroups were prepared from their corresponding alcohols under basic conditions in good yields. The synthesis of a 1,6-C-linked disaccharide was carried out via reaction of a glycosyl chloride with an aldehyde in the presence of samarium(II) diiodide.
A straightforward and scalable method for the synthesis of protected 2-hydroxyglycals is described. The approach is based on the chlorination of carbohydrate-derived hemiacetals, followed by an elimination reaction to establish the glycal moiety. 1,2-dehydrochlorination reactions were studied on a range of glycosyl chlorides to provide suitable reaction conditions for this transformation. Benzyl ether