Allose 6-deoxy-3-0-methyl

Syntheses of 6-Deoxy-2 and 3-0-Methyl-D-allose and Some 6-DeoxyhexopyranosidePhenyl-boronates... 

An isomeric sugar, D-javose, is a constituent of two cardenolide glycosides (strophanthojavoside and antiarojavoside) found (42) in the seeds of Antiaris toxicaria Lesch. Degradative studies indicated (42) that javose had the structure 6-deoxy-2-0-methyl-D-allose (17) and this assignment was confirmed by two stereospecific syntheses. 

Figure 2. Synthesis of 6-deoxy-2-0-methyl-D-allose (javose).

Syntheses of 6-Deoxy-2- and 3-O-methyl-D-allose and Some 6-Deoxyhexopyranoside Phenyl-boronates," J. S. Brimacombe, A. Husain, F. Hunedy, and M. Stacey, Adv. Chem. Sen, No 74 ( Deoxy-sugars") (1968) 56 - 69. 

P2j Z = 2 D = 1.17 R = 0.080 for 3,888 intensities. This is aconfigu-rational analysis of the macrolide antibiotic 23672RP from Streptomyces chryeus. All three sugar residues are pyranoid the conformation of the a-ketose is CX, with Q = 56 pm, 0 = 9° that of the / -D-mycinose (6-deoxy-2,3-di-0-methyl-D-allose) is 4Clt with Q = 59 pm, 0 = 6° and that of the / -L-mycarose (2,6-dideoxy-3-C-methyl-L-riho-hexose) is 1C4, with Q = 53 pm, 0= 177°. The O-5-C-l-O-l-C glycosidic torsion-angles are —71, —87, —83°. The atomic coordinates reported in the paper refer to the opposite enantiomer. 

This interesting transformation from a readily available 6-deoxyhexose forms the basis for the synthesis231 of 6-deoxy-2,3-di-0-methyl-D-allose (mycinose),168 one of the carbohydrate moieties of the antibiotic chalco-mycin. The synthesis merely involves the protection of the C-5 hydroxyl group in (41) by benzylation, followed by partial hydrolysis with acid, methylation of the product at the C-2 and C-3 hydroxyl groups, and debenzylation. 

Subsequently Jeanloz31 was able to convert 2-amino-2-deoxy-D-glucose into 2-amino-2-deoxy-D-allose (VI) by solvolysis of the 3-methylsulfonyl ester of methyl 2-acetamido-4,6-0-benzylidene-2-deoxy-a-D-glucopyrano-side (V). 

Reaction of Methyl 4,6-0-Benzylidene-3-C-methyl-2-0-p-tolylsulfonyI-a-D-allo-pyranoside with Sodium Methoxide in Methyl Sulfoxide Synthesis of 6-Deoxy-3-C-methyl-3-O-methyl-D-allose (2-Hydroxy-D-cladinose), G. B. Howarth, W. A. Szarek, and J. K. N. Jones, Carbohydr. Res., 11 (1969) 257-262. 

Recent applications of this reaction include the reduction of methyl 3-0-benzyl-2-O-methyl-6-O-p-tolylsulfonyl-a-D-allopyranoside, leading to the synthesis of 6-deoxy-2-0-methyl-D-allose, and the reduction of methyl 3-0-methyl-2,6-di-0-p-tolylsulfonyl-a-D-allopyrano-side as a step in the synthesis of 6-deoxy-3-0-methyl-D-allose. The last-named compound was also synthesized, in lower yield (because of competing side-reactions), starting from methyl 3-0-methyl-2,4,6-tri-0-p-tolylsulfonyl-a-D-allopyranoside. 

Methyl ethers of 2-amino-2-deoxy-D-allose have been prepared in order to be subsequently degraded into methyl ethers of n-ribose. Methylation of methyl 2-acetamido-4,6-0-benzylidene-2-deoxy-o -D-alloside gave the 3-methyl ether, which, in turn, was hydrolyzed to afford methyl 2-acetamido-2-deoxy-3-0-methyl-a-D-allopyranoside. After partial methylation, a dimethyl ether, probably the 3,6, was isolated, whereas exhaustive methylation afforded the 3,4,6-trimethyl ether. An identical trimethyl ether was isolated after methylation of methyl 2-acetamido-3,4,6-tri-0-acetyl-2-deoxy-a-n-alloside. Hydrolysis of the methyl glycosides of both the 3-methyl and the 3,4,6-trimethyl ethers gave crystalline hydrochlorides, and the base of the former ether was characterized by means of its crystalline Schiff base with 2-hydroxynaphthaldehyde. 

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