Mannopyranosyl chloride

As part of a study on cell-surface glycans, 2,3-bis(tetradecyloxy)propyl 2-deoxy-2-fluoro-a- and - -D-mannopyranosides were prepared by condensation of 3,4,6-tri-0-benzyl-2-deoxy-2-fluoro-a-D-mannopyranosyl chloride with 2,3-bis(tetradecyloxy)propanol. 

CJ4H19CIO9 Tetra-O-acetyl-a-D-mannopyranosyl chloride TAMANC 37 394... 

C34H26C1209 2,3,4,6-Tetra-O-benzoyl-a-D-mannopyranosyl chloride (TBZMAC)125... 

Kenne and associates (57) have applied this procedure for the synthesis of a-D-mannopyranosyl derivatives linked to L-serine/L-threonine (59 and 60). Compounds 59 and 60 were obtained by coupling 2,3,4,6-tetra-<9-acetyl-D-mannopyranosyl chloride (56) with Fmoc-L-serine benzyl ester or Fmoc-L-threonine benzyl ester in the presence of silver triflate and 4-A molecular sieves, followed by deprotection (57). 

Configurational inversion at C-2 of compound 82 has no major effect on the products of photobromination, tetra-0-acetyl-/ -D-mannopyranosyl chloride giving the C-2 epimers of compounds 84 and 86 in 72 and 12% yield, respectively.25... 

Some of the few literature examples of photochlorination of carbohydrate derivatives relate to compounds of this series. On treatment with sulfuryl chloride in the presence of azobis(isobutanonitrile) in refluxing carbon tetrachloride, tetra-0-acetyl-/ -D-glucopyranosyl and -mannopyranosyl chloride give25 products of monosubstitution of chlorine at C-l and at C-5. 

The same system improves the yields of /J-D-mannopyranosidcs in reaction of 2,3 4,6-di-0-cyclohexylidine-a-D-mannopyranosyl chloride, particularly with carbohydrates with a single free secondary hydroxyl group.2... 

In the chloride series, the benzoate (Figure 1, center), crystallizes in a skew conformation 2Sq( 8). However, the arrangement around the anomeric center corresponds to a tetraaxial conformation, and thus a comparison of distance data should be permissible. In addition, the a-mannopyranosyl chloride recently determined by David et al. (9) is shown in Figure 1. Obviouslv, the distances between C-l and the ring-oxygen atom are about 1.37- -l. 38 and only slightly larger as compared with the fluoro compound. The tetraequatorial, acetylated chloro compound exhibits almost "normal data (10). 

The results could easily be interpreted as Rhind-Tutt and Vernon (4) explained the solvolysis of 2,3,4,6-tetra-O-methyl-a-D-mannopyranosyl chloride shielding of the back... 

In early work on the methanolysis of tetra-O-methyl a-o-glucopyranosyl and -mannopyranosyl chlorides, it was shown that the reactions were cleanly first order whether followed by titration of the acid produced or by polarimetry. The gluco chloride gave exclusively the p-methyl glucoside, the manno an anomeric mixture. Reactions of the gluco but not manno chloride with thiophenoxide ion were cleanly bimolecular and gave exclusive inversion, as expected. 

C12H17CIO7 Tri-O-acetyl-6-deoxy-a-L-mannopyranosyl chloride ADMANC 37 387... 

Regioselective debenzoylation of nucleoside 2, 3 5-tri-O-benzoates using hydrazine hydrate has been reported. With 1 mol reagent in acetic acid-pyridine the 3 5-di-O-benzoyl derivative was produced when the bases were adenine, guanine, or indole, whereas with excess hydrazine hydrate in 1 1 chloroform-methanol, 98% of the 5-O-benzoyl derivative was produced (base = adenine or uracil). 3, 5-Di-O-benzoyl-2-deoxy-nucleosides gave a 90% yield of a 1 1 mixture of 3 - and 5-O-benzoyl nucleosides with 1 mol hydrazine hydrate in pyridine. Treatment of the mannose orthoacetate (5) with benzoyl chloride in pyridine gave 2,3,4,6-tetra-O-acetyl-a-D-mannopyranosyl chloride and ethylbenzoate, whereas the related orthoester of mu co-inositol (6) gave 66% of the correspond-... 

Glycosyl fluorides. 3,4,6-Tri-0 acetyl-2-diloro-2-deoxy-a-D-mannopyranosyl chloride added to a stirred ice-cold soln. of Ag-fluoroborate in anhydrous toluene, and the product isolated after 1 hr. 3,4,6-tri-0-acetyl-2-chloro-2-deoxy-a-D-mannopyranosyl fluoride. Y 91%. F. e. s. K. Igarashi, T. Honma, and J. Irisawa, Carbohydrate Res. 11, fill (1969) 13, 49 (1970). 

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