Glucal synthesis

In 1969, Adamson, Foster, and others - reported the synthesis of 2-deoxy-2-fluoro sugars by addition ofCFjOF (in CFCI3, — 80°) to 3,4,6-tri-O-acetyl-l,5-anhydro-2-deoxy-D-flra/)/>zo-hex-l-enitol (61 3,4,6-tri-O-acetyl-D-glucal). The reagent fluorinates 61 electrophilically - °° at C-2, to afford c/v-addition products trifluoromethyl 3,4,6-tri-C)-acetyl-2-deoxy-2-... 

Introduction of F2 into 3,4,6-tri-O-acetyl-D-glucal (61) in CCI3F (Freon 11) at —78° in a manner used for the non-labeled compound (so-called cold synthesis) gave a 4 1 mixture of 3,4,6-tri-0-acetyl-2-deoxy-2-[ F]fluoro-a-D-gluco- (574) and ) -D-manno-pyranosyl fluorides (575),... 

In addition, Wipf and co-workers104 have used silver(i)-catalyzed addition of zirconocenes to 3,4,6-tri-O-benzyl-D-glucal epoxide 93 for the stereoselective synthesis of a-C-glucosyl compounds 95 and 96 following a similar mechanism as in the reaction with organoaluminium and organoboron reagents (Scheme 32). 

The versatility of this approach was demonstrated in the synthesis of a variety of oligosaccharides (Scheme 2.7). The synthesis of hexasaccharide 30 (Scheme 2.8) exemplified the use of a glucal acceptor with a secondary alcohol (27) as well as the use of a disaccharide acceptor such as 29. These typical, varied systems can be included in the protocol without complications. 

The first problem to be addressed in the solid-phase assembly of Leb involved the synthesis of the core tetrasaccharide (Scheme 2.17).25 Polymer-bound galactal 10 was epoxidized with DMDO. The resultant epoxide reacted with a solution of glucal 55 to give polymer-bound disaccharide diol 56. This reaction proceeded in a highly regioselective fashion, wherein glycosylation occurred only at the allylic C3 position... 

M. Ganesan and N. G. Ramesh, A new and short synthesis of naturally occurring 1-deoxy-L-gulono-jirimycin from tri-O-benzyl-D-glucal, Tetrahedron Lett., 51 (2010) 5574-5576. 

On their side, Yin and Linker [216] made use of a 2-C-branched hexopyranoside, the synthesis of which was achieved by addition of dimethyl malonate to tri-O-benzyl-D-glucal (TUPAC name 3,4,6-tri-0-benzyl-l,5-anhydro-2-deoxy-D-araZtino-hex-l-enitol, Scheme 45) [217], Thus, saponification of the 2-C-[bis(meth-oxycarbonyl)]methyl derivative 184 to the corresponding malonic acid 185 was followed by heating in refluxing toluene. This led to decarboxylation and lactoniza-tion giving 186. The method was optimized and applied to the synthesis of pentoses and disaccharides. 

In a different synthesis of 1,5-anhydrohexitols from a compound having a pyranoid ring, Lehmann and Friebolin31 treated 1,5-anhydro-2-deoxy-D-arafemo-hex-l-enitol (D-glucal) (20) with a-toluenethiol in the presence of light, and obtained l,5-anhydro-2-S-benzyl-2-thio-D-mannitol (21) and the epimeric anhydro-D-glucitol in equal amounts. 

Tri-0-acetyl-l,5-anhydro-2-deoxy-D-arabino-hex-l-enitol (tri-O-acetyl-D-glucal) was the starting point for the synthesis of 1,5-anhy-dro-2-chloro-2-deoxy-D-glucitol or -D-mannitol by way of the 1,2-dichloride (22), which was reduced32 by means of lithium aluminum hydride to the 2-chloro-2-deoxy derivative (23). That the chlorine... 

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