Reactions of Sugar Chlorosulfates: Vii. Some Conformational Aspects

Abstract

The reaction of sulfuryl chloride with several 1,6-anhydro-hexosa~ls has yielded crystalli~le, fully chlorosulfated derivatives. lieplacement of the chlorosulfate moieties by chlorodeoxy groups could not be achieved under the reaction conditions employed. This non-reactivity is discussed in terms of steric interactions in the transition state for substitution.An examination of some chloro-substituted sugar chlorosulfates conhrmed that an axial chlorodeoxy group in a glycopyranoside deactivates a neighboring equatorial chlorosulfate group and thus prevents further chlorodeoxy groups being introduced into such positions. Methyl a-D-altropyra~~oside, methyl a-L-rhamnopyranoside, methyl a-D-lyxopyranoside, L-rhamnose, and D-lyxose were reacted with sulfuryl chloride. The resulting products were those expected if these sugars reacted primarily in the C1 conformation.

Investigation of the base promoted tandem syn-elimination–Favorskii rearrangement of levoglucosan sulfonates

“…From levoglucosan 1 a series of analogues of 5, 19-21, was prepared. Known trimesylate 19 was prepared as described in the literature, 8 while known tris(chlorosulfate) 20 was prepared by an improvement of the literature procedure 14 which allowed its preparation in 80% yield (Scheme 4). The tris(trifluoromethanesulfonate) 21 was prepared in a similar fashion using Tf 2 O (7 eq.)…”

“…We also investigated the reaction of readily available stereoisomers of levoglucosan 26 15 and 28. 16 The chlorosulfates 27 14 and 29 were obtained from 26 and 28 by the same method and with the same yield as the conversion of 1 to 20 (Scheme 5). The Favorskii esters 6 and 24 were observed to undergo dimerisation or oligomerisation on prolonged standing in the dry state, occasionally even during silica gel chromatography or in a chloroform solution.…”

Haworth Memorial Lecture. The sweeter side of chemistry

“…The reaction can be controlled to avoid cyclic sulphate formation by reaction at low temperatures, adjusting the ratio of sulphuryl chloride to pyridine and dilution of the reaction with chloroform. The reaction of sulphuryl chloride with sucrose was observed to give the 6'-chloride [43%; (43)] and then proceed conditions, sulphuryl chloride reacts with sucrose to give the 4,6,1',4',6'pentachloride (47) which on treatment with base is transformed, in common with other chloro-sucroses, into an anhydro derivative, in this case a 3,6;3',6'; 2,l'trianhydro derivative (48) not sweet bitter as quinine,57 and a sample of (46) required for 'testing' was misinterpreted as 'tasting'. Against all predictions, the tetrachloride (46) proved to be several hundred times sweeter than sucrose 56 (Table 2).…”

Synthesis of Paratose (3,6-Dideoxy-D-ribo-hexose) and Tyvelose (3,6-DiAeoxy-D-arabino-hexose)

“…Acid-catalyzed de-0-benzylidenation of compound 1 gave the previously reported (15) methyl 3-chloro-3-deoxy-P-D-allopyranoside (9) as a syrup. Treatment of 9 with sulfuryl chloride yielded a syrup, which, on dechlorosulfation, gave crystalline methyl 3,6-dichloro-3,6-dideoxy-P-D-allopyranoside (1 0) (20). The lack of substitution by chloride ion of the intermediate chlorosulfonyloxy group at C-4 is attributed to the presence of the vicinal axial substituent at C-3; also, a chlorosulfonyloxy group at C-2 is deactivated to nucleophilic substitution by chloride ion (14,15,20,21).…”

“…Treatment of 9 with sulfuryl chloride yielded a syrup, which, on dechlorosulfation, gave crystalline methyl 3,6-dichloro-3,6-dideoxy-P-D-allopyranoside (1 0) (20). The lack of substitution by chloride ion of the intermediate chlorosulfonyloxy group at C-4 is attributed to the presence of the vicinal axial substituent at C-3; also, a chlorosulfonyloxy group at C-2 is deactivated to nucleophilic substitution by chloride ion (14,15,20,21). Hydrogenation of 10, in the presence of potassium hydroxide, over a W-4 Raney nickel catalyst (12), gave crystalline methyl 3,6-dideoxy-P-D-ribohexopyranoside (11).…”