Synthesis of higher-carbon sugars via vinyltin derivatives of simple monosaccharides

6-O-Benzyl-7,8-dideoxy-1,2:3,4-di-O-isopropylidene-l-glycero-α-d-galacto-oct-7-ynopyranose reacted with tributyltin hydride to afford (Z-6-O-benzyl-7,8-dideoxy-1,2:3,4-di-O-isopropylidene-8-(tributylstannyl)-l-glycero-α-d-galacto-oct-7-enopyranose, which was subsequently isomerized to the E-olefin 4. Replacement of the tributyltin moietey with lithium in 4 afforded the vinyl anion which reacted with 3-O-benzyl-1,2-O-isopropylidene-α-d-xylo-pentodialdo-1,4-furanose, furnishing 3-O-benzyl-6-C-[(E)-6-O-benzyl-7-deoxy-1,2:3,4-di-O-isopropylidene-l-glycero-α-d-galacto-heptopyranos-7-ylidene] -60-deoxy-1,2-O-isopropylidene-α-d-gluco- (6) and -β-l-ido-furanose (7) in yields of ∼70 or ∼87% (depending on the temperature of the reaction). The configurations of the new chiral centers in 6 and 7 were determined by their conversion into 3-O-benzyl-1,2-O-isopropylidene-α-d-gluco- and -β-l-ido-furanose, respectively. Oxidation of 6 and 7 gave the same enone, 3-O-benzyl-6-C-[(E)-6-O-benzyl-7-deoxy-1,2:3,4-di-O-isopropylidene-l-glycero-α-d-galacto- heoptopyranos-7-ylidene]-6-deoxy-1,2-O-isopropylidene-α-d-xylo-hexofuranos-5-ulose.     

Synthesis of gem-di-C-substituted derivatives of carbohydrates by way of nucleophilic-addition reactions of aldohexofuranoid 3-C-methylene derivatives

Nucleophilic Michael-type additions to aldohexofuranoid 3-C-methylene derivatives, namely, 3-deoxy-1,2:5,6-di-O-isopropylidene-3-C-nitromethylene-α-d-ribo-hexofuranose and 3-C-[cyano(ethoxycarbonyl)methylene]-3-deoxy-1,2:5,6-di-O-isopropylidene-α-d-ribo-hexofuranose employing phase-transfer catalysis, afforded novel gem-di-C-substituted sugars. The conversion of 3-deoxy-1,2:5,6-di-O-isopropylidene-3-C-methyl-3-C-nitromethyl-α-d-allo-hexofuranose into a 3-C-hydroxymethyl-3-C-methyl derivative with titanium trichloride, and that of the nitromethyl groups of 3-deoxy-1,2:5,6-di-O-isopropylidene-3,3-di-C-nitromethyl-α-d-ribo-hexofuranose, and 3-deoxy-1,2:5,6-di-O-isopropylidene-3-C-methyl-3-C-nitromethyl- and -3-C-nitromethyl-α-d-allo-hexofuranose into cyano groups with phosphorus trichloride in pyridine is also described.     

Routes to higher-carbon sugar derivatives having keto-acetylenic and -alkenic,and α,β-unsaturated aldehyde functionality

Oxidative dimerization of 7,8-dideoxy-1,2:3,4-di-O-isopropylidene-d-glycero-α-d-galacto-oct-7-ynopyranoside (1) gave a high yield of the diyne 2, readily reduced by lithium aluminum hydride to the trans,trans-diene (4). The structures of 2 and 4 were established spectroscopically and by degradation of 4 to d-glycero-d-galacto-heptitol (perscitol). A mixture of the alkyne 1 and its 7-epimer 10 was readily oxidized by dimethyl sulfoxide-acetic anhydride to the 6-ketone 11, and the 8-alkene analog was similarly prepared from the alkenes derived from 1 and 10. Likewise, oxidation of 6,7-dideoxy-1,2-O-isopropylidene-α-d-gluco(and β-L-ido)-hept-6-enopyranose gave the corresponding 5-ketone. The acetylenic ketone 11 gave a crystalline oxime and (2,4-dinitrophenyl)hydrazone, the latter being accompanied by the product of attack of the reagent at the acetylene terminus (C-8). Previous work had shown that formyl-methylenetriphenylphosphorane did not convert 1,2:3,4-di-O-isopropylidene-6-aldehydo-α-d-galacto-hexodialdo-1,5-pyranose into the corresponding C₈ unsaturated aldehyde, although the latter was obtainable via1 and 10 by an ethynylation-hydroboration sequence. The Wittig route with formylmethylenetriphenylphosphorane is shown to be satisfactory for obtaining C₇ unsaturated aldehydes from 3-O-benzyl-1,2-O-isopropylidene-5-aldehydo-α-d-xylo-pentodialdo-1,4-furanose (22) and the 3-epimer of 22, respectively. These reactions provide convenient access to higher-carbon sugars and chiral dienes for synthesis of optically pure products of cyclo-addition reactions.     

Synthesis and crystal structure of 7-acetamido-6,7,8-trideoxy-1,2:3,4-Di-O-isopropylidene-α-d-glycero-d-galacto-octo-pyranose

7-Acetamido-6,7,8-trideoxy-1,2:3,4-di-O-isopropylidene-α-d- and -β-l-glycero-d-galacto-octopyranoses (8) and (9), intermediates for the synthesis of analogs of the antibiotic lincomycin, have been synthesized from cis-6,7,8-trideoxy-1,2:3,4-di-O-isopropylidine-7-C-nitro-α-d-galacto-oct-6-enose (4). The configuration of C-7 in compound 8 was determined by X-ray crystallagraphy. The crystals are orthorhombic, space group P2₁,2₁2₁ with Z4, in a unit cell of dimensions a2.457(1) nm, b1.380(1) nm, and c526(1) pm. The conformation of compound 8 in the solid state is °S₂, slightly distorted towards °H₅.     

Purification and properties of an endo-(1 leads to 3)-beta-D-glucanase from malted barley

3,6-Anhydro-α-D-galactopyranose 1,2-(methyl orthoacetate) and its 4-acetate were synthesized from 2,3,4-tri-O-acetyl-6-O-tosyl-α-D-galactopyranosyl bromide. Condensation of the above-mentioned, acetylated ortho ester with 1,2:3,4-di-O-isopropylidene-α-D-galactopyranose gave 6-O-(2,4-di-O-acetyl-3,6-anhydro-β-D-galactopyranosyl)-1,2:3,4-di-O-isopropylidene-α-D-galactopyranose. The same disaccharide derivative was synthesised from 6-O-β-D-galactopyranosyl-1,2:3,4-di-O-isopropylidene-α-D-galactopyranose by mono-O-tosylation followed by treatment with alkali and acetylation.     

Branched-chain amino sugars. stereospecific synthesis of 3-C-(2-acetamidoethyl)-3-deoxy-1,2-O-isopropylidene-β-l-lyxofuranose

Condensation of 1,2:5,6-di-O-isopropylidene-α-d-xylo-hexofuranos-3-ulose (1) with diethyl cyanomethylphosphonate afforded a mixture of the cis- and trans-3-cyanomethylene-3-deoxy-1,2:5,6-di-O-isopropylidene-α-d-xylo-hexofuranoses (2) in 80% yield. Catalytic reduction of 2 yielded 3-C-cyanomethyl-3-deoxy-1,2:5,6-di-O-isopropylidene-α-d-gulofuranose (4) exclusively. Palladium and hydrogen was found to rearrange the exocyclic double bond of 2 to give the 3,4-ene (3). Catalytic reduction of 3 also proceeded stereospecifically to yield 4. Selective hydrolysis of 4 yielded the diol 5, which was cleaved with periodate and the product reduced with sodium borohydride to afford crystalline 3-C-cyanomethyl-3-deoxy-1,2-O-isopropylidene-β-l-lyxofuranose (6) in 87% yield. Catalytic reduction of the latter with hydrogen and platinum in the presence of acetic anhydride and ethanol gave the crystalline l-amino sugar, 3-C-(2-acetamidoethyl)-3-deoxy-1,2-O-isopropylidene-β-l-lyxofuranose (7) in 92% yield.     

Conformational analysis of 1,2:3,4-di-O-isopropylidene-α-d-galacto-octopyranose derivatives: a 1H- and 13C-N.M.R.-spectral and x-ray comparative study

The pyranoid conformations of 7-acetamido-6,7,8-trideoxy-1,2:3,4-di-O-isopropylidene-d-glycero-α-d-galacto-octopyranose (3) and 7-acetamido-7,8-dideoxy-1,2:3,4-di-O-isopropylidene-l-threo-α-d-galacto-octopyranose (4) in solution have been determined by calculation of the dihedral angles from the vicinal, proton-proton coupling-constants, using three modifications of the Karplus equation. Of these, only the equation ³J(HCCH)(φ)  (7.48  0.74 -ΣδE_x)  (2.03  0.17 ΣE_x)cos φ + (4.60  0.23 ΣδE_x)cos 2φ + 0.06 (Σ ± ΔE_x)sin φ + 0.62 (Σ ± ΔE_x)sin 2φ indicates that the pyranoid part of 3 and 4 has the °S₂ conformation, very slightly distorted towards °H₅, in agreement with the conformations determined for the crystalline state. Analysis of the ¹H-n.m.r. data for a series of 1,2:3,4-di-O-isopropyl-idene-α-d-galacto-octopyranose derivatives shows that the pyranoid parts of these compounds adopt the same conformation as that found for 3 and 4.     

Studies of carbohydrate derivatives having the -CH2F function

The following primary sulphonates have been converted into the corresponding deoxyfluoro derivatives by reaction with potassium fluoride in ethylene glycol:1,2:3,4-di-O-isopropylidene-6-O-tosyl α-D-galactopyranose (1), methyl 2,3-O2-isopropyliden-5-O-tosyl-α,β-D-ribofuranoside (2), 1,2:3,4-di-O-methylene-6-O-tosyl-α-D-glucofuranose (3), 3,5-di-O-benzylidene-1,2-O-isopropylidene-6-O-tosyl-α-D-glucofuranose (4), and 1,2:3,5-di-O-isopropylidene-6-O-tosyl-α-D-glucofuranose (5). The yields were generally poor; in the reaction of 1, a major by-product was 6-O-(2-hydroxyethyl)-1,2:3,4-di-O-isopropylidene-α-D-galactopyranose (11). The reaction of the primary hydroxyl precursor of each of the above tosylates with N2-(2-chloro- 1,1,2-trifluoroethyl)-N,N-diethylamine generally yielded the O-chlorofluoroacetyl derivative; however, 1,2:3,5-di-O-methylene-α-D-glucofuranose (12) was converted into the 6-deoxy-6-fluoro derivative (8). The ¹⁹F resonances of compounds containing the CH₂F moiety fall between φ_C +213 and φ_C +235 p.p.m. The differences between the vicinal¹⁹F-¹H couplings of compounds having the D-gluco and D-galacto configurations clearly reflect the influence of the C-4O-4 substitutents on the populations of the C-5C-6 rotamers. A novel type of noise-modulated, heteronuclear decoupling experiment is described.     

Acetonation of some pentoses with 2,2-dimethoxypropane-N,N-dimethylformamide-p-toluenesulfonic acid

d-Xylose, d-arabinose, and d-ribose were each treated with 2,2-dimethoxypropane in N,N-dimethylformamide containing a trace of p-toluenesulfonic acid. d-Xylose gave 3,5-O-isopropylidene-d-xylofuranose, 1,2:3,5-di-O-isopropylidene-α-d-xylofuranose, 1,2-O-isopropylidene-α-d-xylopyranose, and two acyclic di-O-isopropylidene derivatives. d-Arabinose gave the known 3,4-O-isopropylidene-β-d-arabinopyranose and 1,2:3,4-di-O-isopropylidene-β-d-arabinopyranose. d-Ribose gave 2,3-O-isopropylidene-d-ribofuranose almost exclusively.     

Large scale isolation of 1,2:3,4-di-O-isopropylidene-α-d-glucoseptanose and 2,3:4,5-di-O-isopropylidene-β-d-glucoseptanose

Isolation of 1,2:3,4-di-O-isopropylidene-α-d-glucoseptanose and 2,3:4,5-di-O-isopropylidene-β-d-glucoseptanose from the mother-liquors from commercial scale preparation of 1,2:5,6-di-O-isopropylidene-α-d-glucofuranose is described.     

Synthèse de l'acide 5-acétamido-3,5-didésoxy-4-O-méthyl- d-glycéro-d-galacto-2-nonulosonique (acide 4-O-méthyl-N-acétylneuraminique). Partie II

3-Acetamido-3-deoxy-4,5:6,7-di-O-isopropylidene-d-glycero-d-galacto-heptose diethyl dithioacetal was transformed into 3-acetamido-3-deoxy-4,5:6,7-di-O-isopro-pylidene-2-O-methyl-aldehydro-d-glycero-d-galacto-heptose after O-methylation followed by desulfuration. A Wittig reaction with an excess of [ethoxy(ethoxycarbonyl)-methylene]triphenylphosphorane in the presence of benzoic acid gave a mixture of ethyl 5-acetamido-3.5-dideoxy-2-O-ethyl-6,7:8,9-di-O-isopropylidene-4-O-methyl-d-glycero-d-galacto-non-2-enonate (23 %) and the d-glycero-d-talo (22 %) isomer. An ethoxymercuration-demercuration reaction, followed by acid hydrolysis, converted the former into ethyl 4-O-methyl-N-acetylneuraminate and the latter into the C-4 stereoisomer. 4-O-Methyl-N-acetylneuraminic acid was then obtained in crystalline form, and its structure ascertained by mass spectrometry and ¹H- and ¹³C-nuclear magnetic resonance.     

Über die Synthese partiell benzylierter Zucker

1,2:5,6-Di-O-isopropylidene-α-D-allofuranose (1), 1,2:5,6-di-O-isopropylidene-α-D-glucofuranose (2), and 1,2.3,4-di-O-isopropylidene-α-D-galactopyranose (3) have been separately treated in pyridine solution with trifluoromethanesulphonic anhydride, 2,2,2-trifluoroethanesulphonyl chloride, and pentaflucrobenzenesulphonyl chloride. Both 1 and 2 afforded the anticipated sulphonic esters. Although 3 also gave the 2,2,2-trifluoroethanesulphonic and pentafluorobenzenesulphonic esters, the reaction with trifluoromethanesulphonic anhydride yielded 6-deoxy-1,2:3,4-di-O isopropylidene-6-pyridino-α-D-galactopyranose trifluoromethanesulphonate.     

C-4′-Branched-chain sugar nucleosides: synthesis of isomers of psicofuranine

Photoamidation of 3-O-acetyl-1,2:5,6-di-O-isopropylidene-α-d-erythro-hex-3-enofuranose (1) afforded 3-O-acetyl-4-C-carbamoyl-1,2:5,6-di-O-isopropylidene-α-d-gulofuranose (2) and 3-O-acetyl-3-C-carbamoyl-1,2:5,6-di-O-isopropylidene-d-α-allofuranose (3) in 65 and 26% yields, respectively (based on consumed1). Treatment of2 with 5% hydrochloric acid in methanol yielded the spiro lactone5, which was deacetylated to yield7. Reduction of5 with sodium borohydride afforded 4-C-(hydroxymethyl)-1,2-O-isopropylidene-α-d-gulofuranose (9) in 79% yield. Oxidation of9 with sodium metaperiodate afforded a dialdose that was reduced with sodium borohydride to give 4-C-(hydroxymethyl)-1,2-O-isopropylidene-α-d-erythro-pentofuranose (11) in 88% yield. Treatment of the acetate12, derived from11, with trifluoroacetic acid, followed by acetylation, afforded the branched-chain sugar acetate14. Condensation of the glycosyl halide derived from14 withN⁶-benzoyl-N⁶, 9-bis-(trimethylsilyl)adenine yielded an equimolar anomeric mixture of protected nucleosides15 and16 in 40% yield. Treatment of the latter compounds with sodium methoxide in methanol afforded 9-[4-C-(hydroxymethyl)-β-d-erythro-pentofuranosyl]-adenine (17) and the α-d anomer18. The structure of3 was determined by correlation with the known 5,3′-hemiacetal of 3-C-(hydroxymethyl)-1,2-O-isopropylidene-α,α′-d-ribo-pentodialdose (25).     

Nucleosides LXXXIII. Synthetic studies on nucleoside antibiotics. 11. Synthesis of methyl 4-amino-3,4-dideoxy-β-D-ribo-hexopyranoside and -hexopyranosiduronic acid (derivatives related to the carbohydrate moiety of gougerotin)

Methyl 4-amino-3,4-dideoxy-β-D-ribo-hexopyranoside (17) and its uronic acid (19) were synthesized via a series of reactions starting from 1,2:5,6-di-O-isopropylidene-3-O-tosyl-α-D-glucofuranose. A method suitable for the large scale preparation of 3,4-dideoxy- 1,2:5,6-di-O-isopropylidene-α-D-erythro-hex-3-enofuranose(2) was devised.     

Acid-catalyzed isopropylidenation of some heptoses

Acid-catalyzed acetonation of d-glycero-d-galacto-heptose yields solely the 1,2:3,4:6,7-tri-O-isopropylidene pyranoid derivative, whereas d-glycero-l-gluco- and d-glycero-l-manno-heptose react in the furanose form to give 1,2:5,6-(major) and 1,2:6,7-di-O-isopropylidene-d-glycero-l-gluco-heptose (minor), and 2,3:5,6-(major) and 2,3:6,7-di-O-isopropylidene-d-glycero-l-manno-heptose (minor), respectively.     

Sugar orthocarbonates

A simple procedure is described for preparing sugar orthocarbonates. It is based on treating the corresponding thionocarbonate in pyridine with cupric acetate and an alcohol, such as methanol, ethanol, or isopropyl alcohol. Treatment of 1,2:5,6-di-O-isopropylidene-D-mannitol 3,4-thionocarbonate with diols, such as 1,2-ethanediol, 1,2-propanediol, or 1,2:5,6-di-O-isopropylidene-D-mannitol, also gave orthocarbonates. Methyl thionocarbonate, S-methyl xanthate, and dithiobis(thioformate) derivatives of 1,2:3,4-di-O-isopropylidene-α-D-galactopyranose all gave the trimethyl orthocarbonate upon treatment with methanol in the presence of pyridine and cupric acetate. The structure of the orthocarbonates was proved by elemental analysis, n.m.r., and mass spectra, and by treatment with mild acid to form carbonates. Treatment of 1,2:5,6-di-O-isopropylidene-3-thio-D-altritol 3,4-thionocarbonate with methanol or ethanol gave the corresponding orthothiocarbonate, but on treatment with 1,2-ethanediol or with sodium ethoxide the 3,4-episulfide resulted.     

Photochemical conversion of sugar dimethylthio-carbamates into deoxy sugars

Protected sugar derivatives having one free hydroxyl group may be deoxygenated at the alcoholic position by ultraviolet irradiation of the corresponding dimethylthiocarbamic esters: a concomitant process leads also to the original alcohol. Thus, on photolysis, the 6-dimethylthiocarbamate (1) or 1,2:3,4-di-O-isopropylidene-α-D-galactopyranose (3) gives 6-deoxy- 1,2:3,4-di-O-isopropylidene-α-D-galactopyranose (2) together with 3. Likewise, the 4-dimethylthiocarbamate (6) of 1,6-anhydro-2.3-O-isopropylidene-β-D-mannopyranose (8) gives a mixture of the 4-deoxy derivative 7 and the alcohol 8. 3-Deoxy-1,2:5,6-di-O-isopropylidene-α-D-ribo-hexofuranose (10) was obtained by irradiation of 3-O-(dimethylthiocarbamoyl)-1,2:5,6-di-O-isopropylidene-α-D-glucofuranose (9), and was accompanied by 1,2:5,6-di-O-isopropylidene-α-D-glucofuranose (11). The 3-deoxy-3-iodo analog (14) of 11 underwent conversion into 10 by photolysis, and the deoxy sugar 10 was also prepared from 3,3'-dithiobis(1,2:5,6-di-O-isopropylidene-α-D--glucofuranose) (12) by the action of Raney nickel. Photolysis of the 2-dimethylthiocarbamate (16) of methyl 3,4-O-isopropylidene-β-L-arabinopyranoside (18) gave the 2-deoxy derivative (17), together with the parent alcohol 18, and the same pair of products was obtained by the action of tributylstannane on the 2-(methylthio)thiocarbonyl derivative (19) of 18, although the dimethylthiocarbamate 16 was unreactive toward tributylstannane.     

Photochemical oxidation of partially protected derivatives of α-d-glucofuranose and β-d-fructofuranose

An improved procedure for the preparation of 1,2-O-isopropylidene-β-d-fructofuranose and its 6-pyruvoylation is described. Photolysis of this ester in benzene furnished 5,6-O-isopropylidene-β-d-lyxo-5-ulofuranose, characterised as the O-methyloxime diacetate. Similary, photochemical oxidation of 1 1,2-O-isopropylidene-6-O-pyruvoyl-α-d-glucofuranose gave 1,2-O-isopropylidene-α-d-lgluco-hexodialo1,4:6,3-difuranose in excellent yield.     

Synthesis,crystal structure,and conformation of 1(S)-acetoxy-3-[6(R)-O-benzyl-1,2:3,4-di-O-isopropylidene-α-d-galactopyranos-6-yl]-1-(methyl 2,3,4-tri-O-benzyl-6-deoxy-β-d-galactopyranosid-6-yl)propyne

Condensation of 6-O-benzyl-7,8-dideoxy-1,2:3,4-di-O-isopropylidene-d-glycero-α-d-galacto-oct-7-ynopyranose with methyl 2,3,4-tri-O-benzyl-6-deoxy-β-d-galacto-heptodialdo-1,5-pyranoside afforded a 2:1 mixture of the 1S and 1R isomers (1a and 1b) of 3-[6(R)-O-benzyl-1,2:3,4-di-O-isopropylidene-α-d-galactopyranos-6-yl]-1-hydroxy-1-(methyl 2,3,4-tri-O-benzyl-6-deoxy-β-d-galactopyranosid-6-yl)propyne. A single crystal of the 1-O-acetyl derivative (1c) of 1a was investigated by X-ray diffraction methods in a four-circle diffractometer. Compound 1c crystallises in the monoclinic system, space group P2₁ (Z = 2) with cell dimensions a = 14.896(2), b = 8.295(1), c = 20.547(3) Å, and β = 102.66(1)°. The structure was solved by direct methods and refined by a full-matrix, least-squares procedure against 3839 unique reflections (F > 2σ_F), resulting in a final R = 0.045 (unit weights). The configuration at the new chiral center (C-1) was established as S(d). The galactopyranose rings have conformations ⁴C₁ (tri-O-benzylated moiety) and °S₅ + °T₂ (di-O-isopropylidenated moiety). The 1,2- and 3,4-O-isopropylidene rings have ³T₂ and ²E conformations, respectively.     

Dr. Horace S. Isbell

Addition of ethyl isocyanoacetate in strongly basic medium to the glycosuloses 1,2:5,6-di-O-isopropylidene-α-d-ribo-hexofuranos-3-ulose (1) and 1,2-O-isopropylidene-5-O-trityl-d-erythro-pentos-3-ulose (2) gave the unsaturated derivatives (E)- and (Z)-3-deoxy-3-C-ethoxycarbonyl(formylamino)methylene-1,2:5,6-di-O-isopropylidene-α-d-glucofuranose (3 and 4), and (E)-3-deoxy-3-C-ethoxycarbonyl(formylamino)methylene-1,2-O-isopropylidene-5-O-trityl-α-d-ribofuranose (5). In weakly basic medium, ethyl isocyanoacetate and 1 gave 3-C-ethoxycarbonyl(formylamino)methyl-1,2:5,6-di-O-isopropylidene-α-d-allofuranose (12) in good yield. The oxidation of 3 and 4 with osmium tetraoxide to 3-C-ethoxalyl-1,2:5,6-di-O-isopropylidene-α-d-glucofuranose (17), and its subsequent reduction to 3-C-(R)-1′,2′-dihydroxyethyl-1,2:5,6-di-O-isopropylidene-α-d-glucofuranose (18) and its (S) epimer (19) and to 3-C-(R)-ethoxycarbonyl(hydroxy)methyl-1,2:5,6-di-O-isopropylidene-α-d-glucofuranose (21) and its (S) epimer (22) are described. Hydride reductions of 12 yielded the corresponding 3-C-(1-formylamino-2-hydroxyethyl), 3-C-(2-hydroxy-1-methylaminoethyl), and 3-C-(R)-ethoxycarbonyl(methylamino)methyl derivatives (13, 14 and 16). Catalytic reduction of 3 and 4 yielded the 3-deoxy-3-C-(R)-ethoxycarbonyl-(formylamino)methyl derivative 6 and its 3-C-(S) epimer. Further reduction of 6 gave 3-deoxy-3-C-(R)-(1-formylamino-2-hydroxyethyl)-1,2:5,6-di-O-isopropylidene-α-d-allofuranose (23) which was deformylated with hydrazine acetate to 3-C-(R)-(1-amino-2-hydroxyethyl)-3-deoxy-1,2:5,6-di-O-isopropylidene-α-d-allofuranose (24). The configurations of the branched-chains in 16, 21, and 22 were determined by o.r.d.