Glucoside methyl 6-chloro-6-deoxy

B. Helferich, Uber zwei neue Derivate von- -und (3-Methyl Glucosid, Chem. Ber. 56 1082 (1921). H. J. Jennings and J. K. N. Jones, Reactions of sugar chlorosulfates. (V). Synthesis of chloro-deoxy sugars. Can. J. Chem. 43 3018 (1965). 

Viehe s salt reacts with secondary hydroxy groups to yield the inverted chloro-deoxy compounds. Thus the 3-hydroxy-glucoside (15) gives rise to the 3-chloro-3-deoxy-alloside (16). With methyl <-D-lyxofuranoside the 2-0-carbamoyl-3,5-dichloro-derivative (17) was produced. The products were used in the gynthesis of deoxy and amino sugars using conventional methods. The full paper on the... 

Several other methods for the introduction of halo atoms at C-6 in hexose derivatives have been known since the late 1920s. One of the earlier methods involved the reaction of methyl 2,3,4-tri-0-acetyl-6-0-trityl-a-D-glucopyranoside with phosphorus pentachloride which resulted only in an 8% overall yield of methyl 6-chloro-6-deoxy-a-D-glucoside (57). In contrast, the reaction of methyl 2,3,4-tri-0-acetyl-6-0-trityl-a-D-altropyranoside with phosphorus tribromide and bromine afforded a 73% yield of the corresponding 6-bromo-6-deoxy derivative (91). 

Halogen atoms have been placed at C-6 of substituted 6-deoxy-hexoses by a variety of interesting ways, and the products provide potential routes to 6-deoxyhexoses. Helferich and coworkers 4 reported a low yield of methyl 6-chloro-6-deoxy-a-D-glucoside which they prepared by reaction of the (suitably protected) corresponding 6-trityl ether with phosphorus pentachloride. Sinclair 44 has provided a convenient procedure for the preparation of the 6-chloro derivative in yields of 30-35% by allowing methyl a-D-glucopyranoside to react with sulfur monochloride, SjClj, in N,/V-dimethylformamide. A much better yield (73%) of the 6-bromo derivative was reported1 in the reaction of methyl 2,3,4-tri-O-benzoyl-6-O-trityl-a-D-altroside with phosphorus tribromide and bromine. 

Of incidental interest is the observation that an w-chlorine atom may be replaced by iodine under Oldham and Rutherford s conditions, without affecting secondary sulfonyloxy groups. Thus, Levene and Tipson107 found that 5-chloro-5-deoxy-2,3-di-0-tosyl-uridine affords the corresponding 5-deoxy-5-iodo derivative plus sodium chloride on the other hand, methyl 4-chloro-4-deoxy-2,3,6-tri-0-tosyl-a-D- glucoside gives117 the 4-chloro-4,6-dideoxy-6-iodo derivative. These observations, taken... 

The hydrolyses of methyl 3-bromo- and 3-chloro-3-deoxy-a-D-glucoside and 2-bromo- and 2-chloro-2-deoxy-a-n-altroside have been followed, but the data obtained are insufflcient to permit accurate comparisons to be made. 

---