Stereoselective synthesis of 1,1′-linked α-l-lyxopyranosyl β-d-glucopyranoside, the proposed biosynthetic precursor of the FG ring system of avilamycins

Abstract

0 a disaccharide as a single isomer in 72% yield. Interestingly, the formation of a-glucosides was not observed in any case, regardless of the use of glucose as glycosyl donor or acceptor.

A practical approach to Dideoxy-1,4- and 1,5-iminopentitols from protected sugar hemiacetals

“…Starting from L-xylofuranose derivative 1a [16], the sequence gave the O-benzylated 1,4-imino-D-arabinitol 6a, and from Darabinofuranose 1b [17], the corresponding 1,4-imino-L-xylitol derivative 6b was obtained, both resulting from an inversion of configuration at C-4 upon ring closure. Compound 6a was then deprotected by hydrogenolysis to afford the known D-DAB 7a as its hydrochloride salt The known tri-O-benzyl-L-lyxopyranose 8 [19] was thus prepared in three steps from Llyxose. Reaction with Ellman's (R)-tert-butanesulfinamide was performed at 110 °C to give the desired glycosylamine (SR)-9 readily (Scheme 2).…”

“…Procedure C (P. C). A 5-mL microwave vial under argon atmosphere was charged with 2,3,4-Tri-O-benzyl-L-lyxopyranose 8 [19] (0.1 g, 0.24 mmol), 4 Å activated molecular sieves (0.2 g), (R)-(+)-2-methyl-2-propanesulfinamide (58 mg, 0.48 mmol) and a microwave magnetic stir bar. Dry toluene (2 mL) was inserted and the mixture was stirred during 10 min at 20 °C.…”

Unusually Stable Picoloyl‐Protected Trimethylsilyl Glycosides for Nonsymmetrical 1,1′‐Glycosylation and Synthesis of 1,1′‐Disaccharides with Diverse Configurations

“…[1][2][3] These disaccharides are found as the structural units in natural products such as tunicamycins, [4,5] trehalosamines, [6,7] everninomicins, [8,9] and avilamycins. [10,11] Trehaloseg lycolipids contain a1 a!1'a disaccharide core that is desymmetrized with fatty acids and, on some occasions, functionalized with as ulfate group. [12] Examples of these glycolipids include sulfolipids and trehalosedimycolates of Mycobacterium tuberculosis, [13][14][15][16] trehalose dicorynomycolateso fCorynebacterium sp., [12] and maradolipids of Caenorhabditise legans.…”

“…1'a-disaccharides may exist in a1 ,2-cis b-configuration such as everninomicins [8,9,51] and avilamycins. [10,11] For curiosity,w ea lso investigated the applicability of the Pico-protected TMS glycoside for coupling with the 1,2-cis b-directing mannosyl donor. [52] As ap roof of concept study,P ico protected TMS a-acceptors 7 and 36 were glycosylatedw ith the b-directing thiomannosyl donor 52 at 0 8Cb yu sing 1.3 equiv of Me 2 S 2 -Tf 2 O (Scheme 7a).…”

“…1,1′‐Disaccharides are nonreducing glycosides linked at anomeric centers through two glycosidic bonds . These disaccharides are found as the structural units in natural products such as tunicamycins, trehalosamines, everninomicins, and avilamycins . Trehalose glycolipids contain a 1α→1′α disaccharide core that is desymmetrized with fatty acids and, on some occasions, functionalized with a sulfate group .…”