Hexofuranose preparation

The mass spectra of methyl 3-deoxy-p-v-tkreo-pentopyrano-side, methyl 4-deoxy-j3-T>-thieo-pentopyranoside, and 5-deoxy-fi-D-xylo-furanoside are discussed and compared fragmentation paths are sufficiently different to allow identification on the basis of their mass spectra. On the other hand, the mass spectra of methyl 2- and 3-deoxy-5-O-methyl-f3-i>-erythro-pentofuranosides do not exhibit fragmentation differences. The mass spectra of 3-deoxy-l,2 5,6-di-O-isopropylidene -d-xylo - hexofuranose, 5- deoxy -1,2-0-isopropylidene-D-xy o-hexofuranose, and 6-deoxy-l,2-0-iso-propylidene-D-glucofuranose show prominent differences, even between the 5- and 6-deoxy isomers. The interpretation of the spectra was aided by metastable-ion peaks, mass spectra of DzO-exchanged analogs, and the mass spectrum of an O-isopropylidene derivative prepared with acetone-d6. 

Di-0-isopropylidene-a-D-rtbo-hexofuranos-3-ulose (100) was treated with (chlorofluoromethylene)triphenylphosphorane (prepared by reaction of triphenylphosphine on difluorocarbene generated in situ by reaction of potassium ferf-butoxide with dichloro-fluoromethane), to give cis- and rans-3-C-(chlorofluoromethylene)-3-deoxy-l,2 5,6-di-0-isopropylidene-a-D-ribo- (101 and 103) and -xyfo-hexofuranoses (105 and 107), which, on treatment with lithium aluminum hydride, gave cis- and frans-3-deoxy-3-C-(fluoromethyl)-1,2 5,6-di-O-isopropylidene-a-D-rtbo- (102 and 104) and -xyZo-hexofura-... 

Trideoxy sugars have also been prepared from aldono- 1,4-lactones. Thus, 2-0-benzoyl-3,5,6-trideoxy-a-D,L-t/ira>hexofuranose was obtained (202) from L-rhamnono- 1,4-lactone via the furanone 155. L-Rhamnono-1,5-lac-... 

The strategy for the synthesis of carba-hexofuranoses and -pentofuranoses is summarized in Scheme 16. Five new carbaanalogues of hexofuranoses were synthesized 74, 73 and the enantiomer a-L-mannofuranose, and the a-L and /3-D-glucofuranoses. The carba-analogues of the 5-deoxyhexofuranoses with a-L- and -D-lyxo-, and a-L-xyZo-configurations, which we have also prepared [98b], have recently been described, either with the same configuration, or as the enantiomeric compound, or as a racemic mixture [86]. Several of the hitherto known compounds were now obtained in a crystalline state... 

An investigation of the reduction of chlorodeoxy sugars with lithium aluminum hydride has been reported.68 In one experiment, 3-deuterio-l,2 5,6-di-0-isopropylidene-a-D-allofuranose (197) was prepared, and converted into 3-chloro-3-deoxy-3-deuterio- l,2 5,6-di-0-isopropyl-idene-a-D-glucofuranose (198) by treatment with triphenylphos-phine-carbon tetrachloride reduction with lithium aluminum hydride gave 3-deoxy-3-deuterio-1,2 5,6-di-O-isopropylidene-a-D-r/foo-hexofuranose (199), a result which established that the reduction must have occurred with, retention of configuration at C-3. 

Deoxy-l,2 5,6-di-0-i sopropy1idene-a-D-ri bo-hexofuranose has been prepared by a variety of other methods, the most widely used of which is the Raney nickel reduction of the 3-S-[(methylthio)carbonyl1-3-thioglucofurunose... 

O-methyl-a-D-xyZo-hexofuranose was prepared in 85% yield from 80. 

When either of the two methods in the previous Subsection is employed in order to introduce a phosphino (or phosphinyl) group at C-5 of 5-deoxy-D-xyZo-hexofuranoses, only 5-deoxy-5-phosphino- (or -5-phos-phinyl)- L-idopyranoses are produced for instance, 50 — 60 (and 64) — 63 (and 65), and 73 — 78 — 85 — 88 — 90. Therefore, in order to prepare hexopyranoses of the D-gluco type having phosphorus in the hemiacetal ring, an alternative approach had to be devised. 

This Subsection deals with the preparation of 2 - and 4 -ketohexosyl-purines and -pyrimidines, which have proved to be versatile synthetic intermediates. A 5 -keto derivative of a hexofuranose nucleoside is also described. The synthesis of epoxy-, halogeno-, unsaturated, epimino-, and thio-ketonucleosides will be developed in subsequent Subsections and Sections. 

Photochemical desulfonylation, and acid treatment for removal of the iso-propylidene group, afforded the free sugar 40. Similarly, the 5-deoxygenated analogue from D-galactose, 5-deoxy-L-araZu Ko-hexofuranose (46),101 and 5-de-oxy-D-riZw-hexofuranose (42) were prepared. By invertion of the configuration at C-2 in 42, 5-deoxy-D-araZ>mo-hexofuranose (47) was obtained. Nucleosides of the 5-deoxyhexoses have also been described.102... 

From 3-phospholenes 95, pentofuranose- and hexofuranose-type phospha sugars are prepared. Thus, all four kinds of pentofuranose-type phospha sugars (i.e., xylose, lyxose, ribose, and arabinose) are available from 3-phos-pholene as the starting material. Alkylation of 95 by a Cl unit provides the pentofuranose structure. The alkylation under LDA base and alkyl halides proceeds to give 130 (Table 13), whose czs-dihydroxylation affords 131. The... 

An analogous methyl 2,3-dideoxy-3-C-methylene-a-L-en/thro-hexopyranoside (20) was obtained10 from methyl 4,6-O-benzylidene-2-deoxy-a-L-eri/t/iro-hexopyranosid-3-ulose (19) it was used in the synthesis of olivomycose (see p. 242). There was also reported32,34 the preparation of 3-deoxy-l,2 5,6-di-0-isopropylidene-3-C-methyl-ene-a-D-rifco-hexofuranose (22) from 1,2 5,6-di-0-isopropylidene-a-D-nfeo-hexofuranos-3-ulose (21) in about 60% yield, followed by transformations into branched-chain sugar derivatives, including... 

The formation of the pyridinol is prevented if, in the step 19 to 20, no anion can be eliminated from C-3 this is the case with 5-amino-3,5-dideoxy-l,2-0-isopropylidene-a-D-er /thro-pentofuranose, which, on acid hydrolysis, afFords only the Amadori rearrangement product and no pyridine derivative. The reaction then proceeds, according to the above mechanism, in only one direction from 19. The 3-deoxypentose is prepared, in a manner analogous to the formation of 15, from 3-deoxy-l,2-0-isopropylidene-a-D-riho-hexofuranose through catalytic reduction of the phenylhydrazone of its periodate-oxidation product. ... 

Hanaya, T, Yasuda, K, Yamamoto, H, Yamamoto, H, Stereoselectivity in the preparation of 5,6-dideoxy-5-dimethoxyphosphinyl-D- and -L-hexofuranoses, and an efficient synthesis of 5,6-dideoxy-5-hydroxyphosphinyl-L-galactopyranose (a P-in-the-ring L-fucose analogue). Bull. Chem. Soc. Jpn., 66, 2315-2322, 1993. 

As far as the nitrogen analogs are concerned, l,6-anhydro-(6-aceta-mido-2,3-di-0-acetyl-5,6-dideoxy-/3-D-xf/lo-hexofuranose) (260) was isolated after acetylation of the equilibrium mixture prepared from the corresponding 6-amino-5,6-dideoxyhexofuranose the original mixture also contained the parent sugar and traces of two additional azepine compounds.784... 

C. Pedersen and H. S. Jensen, Preparation of some acetylated deoxy-pento- and -hexofuranoses and their deacetylation, Acta. Chem. Scand, 48 (1994) 222-227. 

Cyclization of 5,6-dideoxv-6-nitro-D-xylo-hexofuranose led to a mixture of myo- and epi-isomers (43) which were separated and converted to the corresponding amino compounds.Examples of the use of the Ferrier reaction for preparing cyclitols and amino-cyclitols from D-glucose and D-glucosamine have been published, e.g., (44)- (45).52... 

Reference to the use of 6-benzylthio-l,2-0-isopropylidene-3-0-methyl-a-D-x> /o-hexofuranose-5-ulose for preparation of other derivatives is made in Chapter 14. 

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