Allose preparation

Intramolecular cycloadditions of chiral nitrones provide a useful tool for the preparation of bioactive heterocyclic compounds.63 Shing et al. demonstrated that 1,3-dipolar cycloaddition of nitrones derived from 3-0-allyl-hexoses is dependent only on the relative configuration at C-2,3, as shown in Scheme 8.16. Thus 3-0-allyl-D-glucose and -D-altrose (both with threo-configuration at C-2,3) produce oxepanes selectively, whereas 3-O-allyl-D-allose and -D-man-nose (both with erythro-configuration at C-2,3) give tetrahydropyranes selectively.80... 

L-Allose phenylosazone, prepared from L-psicose, was decomposed by benzaldehyde to L-allosone, which was converted into L-alloascorbic acid.187... 

Silyl enol ether 139 has also been transformed into D-allose, as shown in Scheme 5. The same methods can be applied to the enantiomeric enol ether derived from camphanate 38, and this allows one to prepare L-allose and its derivatives. Oxidation of 139 with MCPBA in THF (20 °C) led to the product of epoxide acidolysis 147 (69 %) which yielded 148 on heating to 200 °C for 15 min. Addition of 1.1 equiv. of MCPBA converted 148 into lactone 149 which in the presence of MeOH and K2CO3 (20 °C), gave selectively diester 150. Reactions 147... 

Take 0.25 ml of the mixed sugars standard solution, add 0.25 ml allose internal standard solution and 0.5 ml 2 M sulphuric acid, mix and substitute instead of the hydrolysate solution in the above procedure for preparation of alditol acetates. The concentration of sugars should give a linear relationship with peak area over the normal ranges. The GLC determination conditions will depend on the instrument, but the following are suggested ... 

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+...

J. Gelas and D. Horton, Kinetic acetonation of D-galactose, D-allose and D-talose with alkyl propenyl ethers as a preparative route to the 4,6- O-isoptopylidene aldohexopyranoaes, Carbohydr. Res. 77 103 (1979). 

Since deacetylation of LXXXII and subsequent ozonization and treatment with water afforded glyoxal (isolated as the phenylosazone) it followed that the ethylenic linkage must be between carbon atoms 2 and 3.204 Reduction of LXXXII, followed by deacetylation, yields ethyl 2,3-didesoxy-D-alloside (LXXXIII). Alternatively, LXXXI could be converted into 4,6-diacetyl-2,3-didesoxy-D-allose, which on glycosidation as above yielded ethyl 4,6-diacetyl-2,3-didesoxy-D-alloside. In this instance the product was a mixture of isomers, since on deacetylation, two forms (m. p. 72-72.5° and 90°, respectively) were isolated. Derivatives of 2,3-didesoxy-L-ribose81 have been prepared from 3,4-diacetyl-L-arabinal,... 

M. Cerny, J. Stanek, Jr., and J. Pacak, Syntheses with anhydro sugars. 7. Preparation of 4-deoxy-D-rifto-hexose (4-deoxy-D-allose), 4-deoxy-D-(yvo-hexose (4-deoxy-D-mannose) and of their 1,6-anhydro derivatives, Collect. Czech. Chem. Commun., 34 (1969) 1750-1765. 

D. C. Baker, D. Horton, and C. G. Tindall, Jr., Large-scale preparation of d-allose observations on the stereoselectivity of the reduction of l,2 5,6-di-O-isopropylidene-a-D-rSo-hexofuranos-3-ulose hydrate, Carbohyd. Res., 24 (1972) 192-197. 

The synthesis of D-psicose as a colorless sirup ([< ]% + 3.1° in water) by Steiger and Reichstein13 may be regarded as the first authentic preparation of this ketohexose. The Kiliani-Fischer cyanohydrin synthesis furnished D-allonic lactone (VII) from D-ribose. This lactone, on reduction with sodium amalgam, gave D-allose (VIII) which was transformed into D-psicose (I) by refluxing with pyridine. Pyridine had been introduced into the Lobry de Bruyn-Van Ekenstein reaction by Fischer, Danilov and their coworkers.13 ... 

Moderate asymmetric induction and low yields are observed when the compound 5, prepared from (A, )-hexadienal and (15,25)-pseudoephedrine, undergoes cycloaddition with the nitroso derivative 6. The major cycloadduct 7 is obtained together with minor amounts of diastereomers (d.r. 62 24 11 3) and after chromatography is isolated in 32% yield. Its configuration is first assigned by H NMR, and then by conversion into the known (+ )-(S)-2-methyl-l-(4-toluenesulfonyl)piperidine. Compound 7 is the key intermediate for the total synthesis of an amino allose derivative135. 

The conversion of calcium o-altronate to n-altrose follows the standard procedure of Fischer, which consists in liberating the aldonic acid, heating it to effect lactonization, and reducing the sirupy lactone with sodium amalgam. Levene and Jacobs thus prepared n-altrose as a sirup, but did not record its rotation. It formed a crystalline phenylosazone, which is common to both n-altrose and n-allose, and a characteristic benzylphenylhydrazone. Pertinent data on these substances, and on ... 

Crystalline L-altrose was described in 1934 by Austin and Humoller. After improving the methods for the preparation of L-ribose," they applied the cyanohydrin synthesis to 30 g. of that sugar and obtained 17 g. of crystalline calcium L-altronate and 14.5 g. of crystalline L-allono-7-lactone. Reduction of the latter with sodium amalgam yielded crystalline L-allose. The calcium L-altronate, by appropriate reactions, was converted to L-altrose, and the last of the sixteen theoretically possible aldohexoses had been prepared. Data on L-altrose and its derivatives are included in Table I. 

From L-allulose Steiger " prepared the phenylosazone (L-allose phenyl-osazone), which was hydrolyzed to L-allosone (LXIV) by means of benzaldehyde. The addition of hydrocyanic acid to the osone, followed by saponification with hydrochloric acid, then yielded crystalline l-alloascorbic acid (LXV), of m. p. 177° (decomp.) and - -29.3° in... 

R, = OH, Rj = H, R2 = OH, R4 = CHjOH in Table 3), the enantiomeric compound of the one just reported could be easily prepared. Aldol condensation products were obtained as diastereomeric mixtures from L-sugars, such as L-fucose, L-xylose, L-lyxose, and o-sugars epimeric to o-mannose relative to the 3-position, such as D-allose and o-gulose [46-48]. Table 4 lists the corresponding aldol condensation products isolated as diastereomeric mixtures. Also, 3-deoxy-D-mannose by condensation with pyruvate gave a diastereomeric mixture of 6-deoxy-KDN furanose derivatives [43]. All these results confirm that sialic acid aldolase, similar to other aldolases, exhibits broad specificity toward the electrophilic acceptor on the other hand, only pyruvate was reported acceptable as the donor [10]. But very recently, in contradiction to that, 3-fluoro-Neu5Ac and 3-fluoro-KDN could be prepared by the sialic acid aldolase-catalyzed condensation of 3-fluoropyruvate and Af-acetylmannosamine or o-mannose (Scheme 5) [47]. 

Recently, the rapid preparation of carbohydrates has been facilitated by a synthetic route based on aldol coupling of three aldehydes used for the de novo production of polyol differentiated hexoses in only two chemical steps. The dimerization of alpha-oxyaldehydes, catalyzed by L-proline, is followed by a tandem Mukaiyama aldol addition-cyclization step catalyzed by a Lewis acid. Differentially protected glucose, allose, and mannose stereoisomers can each be selected, in high yield [46]. Microwave irradiation is becoming an increasingly popular method of carbohydrate synthesis and has been the subject of a recent review [47]. 

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