Allose, 6-deoxy

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. 

Deoxy-p-D-xy/o-hexopyranose 2-Deoxy-D-ribo-hexose not 2-deoxy-D-allose not 4-deoxy-p-D-galactopyranose... 

Cyclohexyl-4 deoxy-4-(hydroxymethyl)-D-allose [oxygen (in CH2OH) has priority over carbon (in cyclohexyl) at C-4] or (4fl)-4-cyclohexyl-4-deoxy-4-(hydroxymethyl)-D-ribo-hexose... 

Mycarose Mycinose Neuraminic acid (Neu) 2,6-D ideoxy-3- C-methy I-l- ribo- hexose 6-Deoxy-2,3-di-Omethyl-D-allose 5-Amino-3,5-dideoxy-D-g/ycero-D-ga/acfo-non-2-ulosonic acid... 

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. 

R. Ashique, R.V. Chirakal, D.W. Hughes, G.J. Schrobilgen, Two-step regio- and stereoselective syntheses of [F-19]- and [F-18]-2-deoxy-2-(R)-fluoro-beta-D-allose, Carbohyd. Res. 341 (2006) 457-466. 

The preparation of 6,6,6-trifluoro analogs of d-rhamnose and 6-deoxy-d-allose from the same furanol derivatives with a CF3 group was achieved by the application of the 1,2-0,0-silyl migration strategy shown in Scheme 8. 

Scheme 8. Preparation of 6,6,6-Trifluoro Analogs of D-Rhamnose and 6-Deoxy-D-allose. (a) DIBALH (b) KOBiT (c) MeOH, H+ (d) KMn04, cat. 18-crown-6 (e) Ac20, pyr. (f) TBAF (g) Ac20 (h) Me2C(OMe)2,H+...

Removal of the hydroxyl group from C-2 of a hexose also increases the furanose content for example, allose, 8% and 2-deoxy-rtho-hexose, 27%. The hydroxyl groups on C-2 and C-3 are cis in allose there is therefore a substantial interaction between vicinal, cis-hydroxyl groups in furanoses. This interaction has been estimated70 to be 3.6 kj/mol. Even when the hydroxyl groups on C-2 and C-3 are trans, there is some increase in the furanose content on removal of OH-2 for example, galactose, 6% 2-deoxy-Zj/xo-hexose, 16% (Table II). 

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. 

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