Glycosyl Dithiocarbamates: β-Selective Couplings without Auxiliary Groups

Abstract

In this article, we evaluate glycosyl dithiocarbamates (DTCs) with unprotected C2 hydroxyls as donors in β-linked oligosaccharide synthesis. We report a mild, one-pot conversion of glycals into β-glycosyl DTCs via DMDO oxidation with subsequent ring opening by DTC salts, which can be generated in situ from secondary amines and CS2. Glycosyl DTCs are readily activated with Cu(I) or Cu(II) triflate at low temperatures and are amenable to reiterative synthesis strategies, as demonstrated by the efficient construction of a tri-β-1,6-linked tetrasaccharide. Glycosyl DTC couplings are highly β-selective despite the absence of a preexisting C2 auxiliary group. We provide evidence that the directing effect is mediated by the C2 hydroxyl itself via the putative formation of a cis-fused bicyclic intermediate.

Chemical O‐Glycosylations: An Overview

“…Glycosyl dithiocarbamates (DTCs) have been used for glycosylations to give β ‐selective products upon being activated by Cu I or Cu II triflates . They have been specifically used for glycosides with no protecting group in the C‐2 position.…”

Practical Synthesis of Aromatic Dithiocarbamates

“…In principle, DTCs can be prepared from their corresponding amines under mildly basic conditions, if the latter is sufficiently nucleophilic. [3,6,15] However, diphenylamine (p K a ~ 25) [25] and related aromatic amines are insufficiently reactive toward CS 2 , and thus require generation of their conjugate base. In the cases of diphenylamine and bis( p -bromophenyl)amine 3 , deprotonation with n -BuLi or n -BuLi/DMSO (dimsyl-Li) followed by addition of CS 2 was sufficient to produce lithium salts of N,N -diphenyl DTC ( 9 ) and N,N -bis ( p -bromophenyl) DTC ( 10 ) respectively, which were isolated in good yields by precipitation with Et 2 O (Table 2, entries 1–4).…”

“…Dithiocarbamates (DTCs) are important precursors for a wide range of chemical applications, [1] such as intermediates in the chemical synthesis of biologically active compounds and natural products, [2,3] as ligands in coordination chemistry to stabilize various transition metals, [4] and as initiators in the vulcanization of rubber and in the synthesis of polymers by reversible addition-fragmentation (RAFT) processes. [5] Dithiocarbamates can also serve as ligands for novel applications in surface chemistry.…”

O-Glicosídeos 2,3-Insaturados: Aplicações, Rearranjo De Ferrier E Reações

“…1 Dentre essas moléculas destacam-se os glicais. 2 Sabe-se também que os glicais são carboidratos largamente utilizados na síntese de O-glicosídeos, [3][4][5][6][7][8][9][10] C-glicosídeos, [11][12][13][14][15][16][17][18] S-glicosídeo, [19][20][21][22][23][24][25][26] e N-glicosídeos [27][28][29][30][31] (Figura 1); e vários tipos de oligossacarídeos. 32 Os mesmos servem como blocos de construção essenciais para síntese de 2-desoxi-hexoses e 2-desoxi-2-amino-hexoses e para síntese de produtos naturais oticamente ativos.…”