Synthesis of 5,6-dideoxy-3-O-methyl-5-C-(phenylphosphinyl)-d-glucopyranose and its 1,2,4-triacetate

Methyl phenylphosphonite or dimethyl phosphite underwent acid-catalyzed addition reactions with some hexofuranos-5-ulose 5-(p-tolylsulfonylhydrazones) (7, 9, and 16), to give the corresponding adducts, 17, 18, 19, and 21. The isomer ratios of the adducts were affected by a 3-substituent in the hydrazones. Treatment of adduct 21 with sodium borohydride and sodium dihydrobis(2-methoxyethoxy)-aluminate (SDMA), followed by acid hydrolysis, gave 5,6-dideoxy-3-O-methyl-5-C-(phenylphosphinyl)-d-glucopyranose (26), which was acetylated to give the 1,2,4-tri-O-acetyl derivatives 27a and 27b. Conformational analysis of compound 27a by X-ray crystallography revealed that the compound was 1,2,4-tri-O-acetyl-5,6-dideoxy-3-O-methyl-5-C-[(S)-phenylphosphinyl]-β-d-glucopyranose in the ⁴C₁(d) form having all substituents equatorial.     

Synthesis of a 6-c-nitro-d-glucopyranose derivative having phosphorus in the hemiacetal ring

5,6-Dideoxy-6-C-nitro-5-(phenylphosphino)-d-glucopyranose was prepared by addition of phenylphosphine to 3-O-acetyl-5,6-dideoxy-1,2-O-isopropylidene-6-C-nitro-α-d-xylo-hex-5-enofuranose, followed by hydrolysis of the resulting 3-O-acetyl-5,6-dideoxy-1,2-O-isopropylidene-6-C-nitro-5-(phenylphosphino)-d-glucofuranose (10). Acetylation of 10 gave the crystalline 1,2,3,4-tetraacetate (16). 5,6-Dideoxy-6-C-nitro-5-(phenylphosphinyl)-d-glucopyranose (15) was obtained by oxidation of 10, and hydrolysis of the resulting 5-phenylphosphinyl compound. Acetylation of 15 gave the 1,2,3,4-tetraacetate (17). Although the n.m.r. spectrum of 17 was complex, the n.m.r. spectrum of 16 was rather simple. The n.m.r. data showed that 16 is the α anomer in the ⁴C₁(d) conformation.     

Synthesis of 2-O-(2-acetamido-2-deoxy-β-D-glucopyranosyl)-D-mannose,and its interaction with D-mannose-specific lectins

Condensation of 3,4:5,6-di-O-isopropylidene-D-mannose dimethyl acetal with 2-methyl-(3,4,6-tri-O-acetyl- 1,2-dideoxy-α-D-glucopyrano)-[2′, 1′:4,5]-2-oxazoline in the presence of a catalytic amount of p-toluenesulfonic acid afforded crystalline 2-O-(2-acetamido-3,4,6-tri-O-acetyl-2-deoxy-β-D-glucopyranosyl)-3,4:5,6-di-O-isopropylidene-D-mannose dimethyl acetal (3) in 25% yield. Catalytic deacetylation of 3 with sodium methoxide, followed by hydrolysis with dilute sulfuric acid, gave 2-O-(2-acetamido-2-deoxy-α-D-glucopyranosyl)-D-mannose (4). Treatment of 3 with boiling 0.5% methanolic hydrogen chloride under reflux gave methyl 2-O-(2-acetamido-2-deoxy-β-D-glucopyranosyl)-α-D-mannopyranoside (5) and methyl 2-O-(2-acetamido-2-deoxy-β-D-glucopyranosyl)-α-D-mannofuranoside (6). The inhibitory activities of 4, 5, and 6 against the hemagglutinating and mitogenic activities of Lens culinaris and Pisum sativum lectins and concanavalin A were assayed. From the results of these hapten inhibition studies, subtle differences of specificity between these D-mannose-specific lectins were confirmed.     

Synthesis of 1,2,4-tri-O-acetyl-5-deoxy-5-C-[(R and S)-methoxy-phosphinyl]-3-O-methyl-α- and -β- d-xylopyranose,and their structural analysis by 400-MHz,proton nuclear magnetic resonance spectroscopy

5-Deoxy-5-iodo-1,2-O-isopropylidene-3-O-methyl-α- d-xylofuranose, prepared quantitatively from its 5-Op-tolylsulfonyl precursor, readily gave the 5-C-(diethoxy-phosphinyl) derivative. Treatment of this compound with sodium dihydrobis(2-methoxyethoxy)aluminate, followed by hydrogen peroxide, mineral acid, and hydrogen peroxide, yielded 5-deoxy-5-C-(hydroxyphosphinyl)-3-O-methyl-α,β- d-xylopyranoses in 65% overall yield. The structures of these sugar analogs were effectively established on the basis of the mass and 400-MHz, ¹H-n.m.r. spectra of the four title compounds, derived by treatment with diazomethane and then acetic anhydride in pyridine. 5-C-[(S)-(1-Acetoxyethenyl)phosphino]-1,2,4-tri-O-acetyl-5-deoxy-3-O-methyl-β- d-xylopyranose was also isolated and characterized.     

An approach to the synthesis of branched-chain amino sugars from c-methylene sugars

The reaction of 1,2:5,6-di-O-isopropylidene-3-C-methylene-α-D-ribo-hexofuranose (4) with mercuric azide in hot 50% aqueous tetrahydrofuran yielded, after reductive demercuration, 3-azido-3-deoxy-1,2:5,6-di-O-isopropylidene-3-C-methyl-α-D-glucofuranose (5). Partial, acid hydrolysis of5 afforded the diol7, which gave 3-azido-3-deoxy-1,2-O-isopropylidene-5,6-di-O-methanesulphonyl-3-C-methyl-α-D-glucofuranose (8) on sulphonylation. On hydrogenation over a platinum catalyst and N-acetylation, the dimethanesulphonate 8 furnished 3,6-acetylepimino-3,6-dideoxy-1,2-O-isopropylidene-5-O-methanesulphonyl-3-C-methyl-α-D-glucofuranose (9), which was also prepared by an analogous sequence of reactions on 3-azido-3-deoxy-1,2-O-isopropylidene-5-O-methanesulphonyl-3-C-methyl-6-O-toluene-p-sulphonyl-α-D-glucofuranose (13). The formation of the N-acetylepimine 9 establishes the D-gluco configuration for 5.1,2-O-Isopropylidene-3-C-methylene-α-D-ribo-hexofuranose (20) reacted with mercuric azide in aqueous tetrahydrofuran at ≈85° to give 3,6-anhydro-1,2-O-isopropylidene-3-C-methyl-α-D-glucofuranose (22) as a result of intramolecular participation by the C-6 hydroxyl group in the initial intermediate.     

Synthesis of acetylenic sugars and uronic acids via two-carbon chain extension of d-ribose

Treatment of methyl β-d-ribofuranoside with acetone gave methyl 2,3-O-isopropylidene-β-d-ribofuranoside (1, 90%), whereas methyl α-d-ribofuranoside gave a mixture (30%) of 1 and methyl 2,3-O-isopropylidene-α-d-ribofuranoside (1a). On oxidation, 1 gave methyl 2,3-O-isopropylidene-β-d-ribo-pentodialdo-1,4-furanoside (2), whereas no similar product was obtained on oxidation of 1a. Ethynylmagnesium bromide reacted with 2 in dry tetrahydrofuran to give a 1:1 mixture (95%) of methyl 6,7-dideoxy-2,3-O-isopropylidene-β-d-allo- (3) and -α-l-talo-hept-6-ynofuranoside (4). Ozonolysis of 3 and 4 in dichloromethane gave the corresponding d-allo- and l-talo-uronic acids, characterized as their methyl esters (5 and 6) and 5-O-formyl methyl esters (5a and 6a). Ozonolysis in methanol gave a mixture of the free uronic acid and the methyl ester, and only a small proportion of the 5-O-formyl methyl ester. Malonic acid reacted with 2 to give methyl 5,6-dideoxy-2,3-O-isopropylidene-β-d-ribo-trans-hept-5-enofuranosiduronic acid (7).     

The deamination of methyl 5-amino-5,6-dideoxy-2,3-O-isopropylidene-α-L-talo- and -β-D-allo-furanoside with nitrous acid

Deamination of methyl 5-amino-5,6-dideoxy-2,3-O-isopropylidene-α-L-talofuranoside (6) with sodium nitrite in 90% acetic acid at ≈0° gave methyl 6-deoxy-2,3-O-isopropylidene-α-L-talofuranoside (8a) and methyl 6-deoxy-2,3-O-isopropylidene-β-D-allofuranoside (9a) (combined yield, 12.3%), the corresponding 5-acetates 8b (2.9%) and 9b (26.4%), and the unsaturated sugar methyl 5,6-dideoxy-2,3-O-isopropylidene-β-D-ribo-hex-5-enofuranoside (10) (43.5%). Similar deamination of methyl 5-amino-5,6-dideoxy-2,3-O-isopropylidene-β-D-allofuranoside (7) gave 8a and 9a (combined yield, 20.4%), 8b (12.5%), 9b (25.8%), 10 (7.7%), and the rearranged products 6-deoxy-2,3-O-isopropylidene-5-O-methyl-L-talofuranose (13a, 17.5%) and the corresponding 1-acetate 13b (14.1%). A synthesis of 13a was accomplished by successive methylation and debenzylation of the conveniently prepared benzyl 6-deoxy-2,3-O-isopropylidene-α-L-talofuranoside (15b). Differences between the two sets of deamination products can be rationalized by assuming that the carbonium-ion intermediate reacts in the initial conformation assumed, before significant interconversion to other conformations occurs.     

Syntheses of 3-O-(2-acetamido-2-deoxy-β-d-glucopyranosyl)-α-d-galactopyranose (“lacto-N-biose II”) and 3,4-di-O-(2-acetamido-2-deoxy-β-d-glucopyranosyl)-d-galactopyranose

3- O-(2-Acetamido-2-deoxy-β-d-glucopyranosyl)-α-d-galactopyranose (10, “Lacto-N-biose II”) was synthesized by treatment of benzyl 6-O-allyl-2,4-di-O-benzyl-β-d-galactopyranoside with 2-methyl-(3,4,6-tri-O-acetyl-1,2-dideoxy-α-d-glucopyrano)[2,1-d]-2-oxazoline (5), followed by selective O-deallylation, O-deacetylation, and catalytic hydrogenolysis. Condensation of 5 with benzyl 6-O-allyl-2-O-benzyl-α-d-galactopyranoside, followed by removal of the protecting groups, gave 10 and a new, branched trisaccharide, 3,4-di-O-(2-acetamido-2-deoxy-β-d-glucopyranosyl)-d-galactopyranose (27).     

Synthesis of 5-deoxy-d-xylo-hexose and 5-deoxy-l-arabino-hexose,and their conversion into adenine nucleosides

Anti-Markovnikov hydration of the olefinic bond of 5,6-dideoxy-1,2-O-isopropylidene-3-O-p-tolylsulfonyl-α- d-xylo-hex-5-enofuranose (4) and methyl 5,6-dideoxy-2,3-di-O-p-tolylsulfonyl-α-l-arabino-hex-5-enofuranoside (11) by the addition of iodine trifluoroacetate, followed by hydrogenation in the presence of a Raney nickel catalyst in ethanol containing triethylamine, afforded 5-deoxy-1,2-O-ísopropylidene-3-O-p-tolylsulfonyl-α-d-xylo-hexofuranose (6) and methyl 5-deoxy-2,3-di-O-p-tolylsulfonyl-α-d-arabino-hexofuranoside (14), respectively. 5-deoxy-d-xylo-hexose and 5-deoxy-l-arabino-hexose were prepared from 6 and 14, respectively, by photolytic O-detosylation and acid hydrolysis. Syntheses of 9-(5-deoxy-β-d-xylo-hexofuranosyl)-adenine and 9-(5-deoxy-α-l-arabino-hexofuranosyl)adenine are also described. Application of the sodium naphthalene procedure, for O-detosylation, to 11 is reported in connection with an alternative synthetic route to methyl 5-deoxy-α-l-arabino- hexofuranoside.     

Oxazoline synthesis of 1,2-trans-2-acetamido-2-deoxyglycosides. Glycosylation with 2-methyl-(3,4,6-tri-O-acetyl-1,2-dideoxy-α-D-galactopyrano)-[2′,1′:4,5]-2-oxazoline

The glycosylating activity of 2-methyl-(3,4,6-tri-O-acetyl-1,2-dideoxy-α-D-galactopyrano)-[2′,1′:4,5]-2-oxazoline has been tested in reaction with partially protected saccharides having free primary or secondary hydroxyl groups or with hydroxy amino acids. 3-O-(2-Acetamido-3,4,6-tri-O-acetyl-2-deoxy-β-D-galactopyranosyl)-N-benzyloxycarbonyl-L-serine benzyl ester (3), 6-O-(2-acetamido-2-deoxy-β-D-galactopyranosyl)-D-galactopyranose (5), p-nitrophenyl 2-acetamido-6-O-(2-acetamido-2-deoxy-β-D-galactopyranosyl)-2-deoxy-β-D-glucopyranoside (7), 6-O-(2-acetamido-2-deoxy-β-D-galactopyranosyl)-D-glucose (9), and 3-O-(2-acetamido-2-deoxy-β-D-galactopyranosyl)-D-glucose (11) were synthesized in high yield.     

Synthesis of 1-deoxy-3-C-methyl-d-fructose and 1-deoxy-3-C-methyl-d-sorbose

Hydroxylation of trans-1,3,4-trideoxy-5,6-O-isopropylidene-3-C-methyl-d-glycero-hex-3-enulose with osmium tetraoxide gave a mixture of 1-deoxy-5,6-O-isopropylidene-3-C-methyl-d-arabino- and -d-xylo-hexulose that was partially resolved by acetonation to give 1-deoxy-2,3:4,5-di-O-isopropylidene-3-C-methyl-β-d-fructopyranose (4), 1-deoxy-3,4:5,6-di-O-isopropylidene-3-C-methyl-keto-d-fructose (5), and 1-deoxy-2,3:4,6-di-O-isopropylidene-3-C-methyl-α-d-sorbofuranose (6). Treatment of a mixture of 4 and 5 with sodium borohydride gave, after column chromatography, 4 and 1-deoxy-3,4:5,6-di-O-isopropylidene-3-C-methyl-d-manno- and -d-gluco-hexitol. Deuterated derivatives corresponding to 4–6 were obtained when isopropylidenation was carried out with acetone-d₆. Deacetonation of 4 and 5 yielded 1-deoxy-3-C-methyl-d-fructose, and 6 similarly afforded 1-deoxy-3-C-methyl-d-sorbose.     

New syntheses of methyl 4,6-O-benzylidene-2-deoxy-3-C-methyl-α-d-arabino-hexopyranoside and its conversion into d-evermicose

Methyl 4,6-O-benzylidene-2-deoxy-3-C-methyl-α-d-arabino-hexopyranoside (4) was prepared from methyl 4,6-O-benzylidene-2,3-dideoxy-3-C-methylene-α-d-erythro-hexopyranoside (1b) and from methyl 4,6-O-benzylidetic-3 C-methyl-α-d-gluco-hexopyranoside (6a) by two different methods. Synthesis of d-evermicose3 (10 (2,6-dideoxy-3-C-methyl-d-arabino-hexose) was then achieved in four steps from 4.     

Conversion of allyl 2-acetamido-2-deoxy-β-d-glucopyranoside into 2-methyl-(3,4,6-tri-O-benzoyl-1,2-dideoxy-α-d- galactopyrano)-[2′,1′:4,5]-2-oxazoline

2-Methyl-(3,4,6-tri-O-benzoyl-1,2-dideoxy-α-d-galactopyrano)-[2′,1′:4,5]-2-oxazoline (7) was prepared from 1-propenyl 2-acetamido-3,4,6-tri-O-benzoyl-2- deoxy-β-d-galactopyranoside (6). The latter was prepared from allyl 2-acetamido-2-deoxy-β-d-glucopyranoside (1) through selective benzoylation at O-3 and O-6, conversion into the 4-p-bromobenzenesulfonate 4, inversion of configuration at C-4 to afford allyl 2-acetamido-3,4,6-tri-O-benzoyl-β-d-galactopyranoside (5), and subsequent isomerization with palladium-charcoal to give 6.     

Synthesis of N-[2-O-(2-acetamido-2,3-dideoxy-5-thio-d-glucopyranose-3-yl)-d-lactoyl]-l-alanyl-d-isoglutamine

N-[2-O-(2-Acetamido-2,3-dideoxy-5-thio-d-glucopyranose-3-yl)-d-lactoyl]-l-alanyl-d-isoglutamine, in which the ring-oxygen atom of the sugar moiety in N-acetylmuramoyl-l-alanyl-d-isoglutamine (MDP) has been replaced by sulfur, was synthesized from 2-acetamido-2-deoxy-5-thio-α-d-glucopyranose (1). O-Deacetylation of the acetylated acetal, derived from the methyl α-glycoside of 1 by 4,6-O-isopropylidenation and subsequent acetylation, gave methyl 2-acetamido-2-deoxy-4,6-O-isopropylidene-5-thio-α-d-glucopyranoside (4). Condensation of 4 with l-2-chloropropanoic acid, and subsequent esterification, afforded the corresponding ester, which was converted, viaO-deisopropylidenation, acetylation, and acetolysis, into 2-acetamido-1,4,6-tri-O-acetyl-2-deoxy-3-O-[d-1-(methoxycarbonyl)ethyl]-5-thio-α-d-glucopyranose (12). Coupling of the acid, formed from 12 by hydrolysis, with the methyl ester of l-alanyl-d-isoglutamine, and de-esterification, yielded the title compound.     

The synthesis of 4′,6′-diacetamido-4′,6′-dideoxycellobiose hexa-acetate from lactose

Reaction of methyl 4′,6′-di-O-mesyl-β-lactoside pentabenzoate (8), synthesised via the 4′,6′-O-benzylidene derivative (6), with sodium azide in hexamethylphosphoric triamide gave three products. In addition to the required 4′,6′-diazidocellobioside (9), an elimination product, methyl 4-O-(6-azido-2,3-di-O-benzoyl-4,6-dideoxy-α-L-threo-hex-4-enopyranosyl)-2,3,6-tri-O-benzoyl-β-D-glucopyranoside (12), and an unexpected product of interglycosidic cleavage, methyl 2,3,6-tri-O-benzoyl-β-D-glucopyranoside (13), were formed. The origin of the latter product is discussed. The diazide 9 was converted into 4′,6′-diacetamido-4′,6′-dideoxycellobiose hexa-acetate (16) by sequential debenzoylation, catalytic reduction, acetylation, and acetolysis.     

A facile synthesis of nucleoside derivatives of 1,4-oxathiane

Adenosine-5′-carboxaldehyde (1a) was treated with nitromethane under alkaline conditions, to give the two stereoisomeric 5′-C-(nitromethyl) derivatives (2 and 3) of adenosine. Catalytic hydrogenation of 2 gave 9-(6-amino-6-deoxy-β-D-allofuranosyl)adenine (4), which, on treatment with nitrous acid, yielded 9-(β-D-allofuranosyl)hypoxanthine (6). Similar treatment of 3 gave the α-L-talo nucleosides 5 and 7. Reaction of 2′,3′-O-p-anisylidene adenosine-5′-carboxaldehyde (1b) with ethoxycarbonylmethylene-triphenylphosphorane afforded 9-(ethyl 5,6-dideoxy-β-D- ribo-hept-5-enofuranosyluronate)adenine (8), which was hydrolyzed to the corresponding uronic acid (9). Catalytic hydrogenation of 8 gave 9-(ethyl 5,6-dideoxy-β-D-ribo-heptofuranosyluronate)adenine (10). Reduction of 8 with lithium aluminum hydride yielded two new analogs of adenosine: 9-(5,6-dideoxy-β-D-ribo-heptofuranosyl)adenine (12) and 9-(5,6-dideoxy-β-D-ribo-hept-5-enofuranosyl)adenine (13).     

A novel synthesis of 2-deoxy-α-glycosides

The key step of the synthesis involves the reaction of glycals [3,4,6-tri-O-acetyl-d-glucal (1), the new glycal derivative 4-O-acetyl-1,5-anhydro-2,6-dideoxy-3-C-methyl-3-O-methyl-l-ribo-hex-l-enitol (2), and 3-acetamido-4,6,-di-O-acetyl-1,5-anhydro-2,3-dideoxy-d-arabino-hex-l-enitol (3)] with 1.5 molar equivalents of several alcohols in the presence ofN-bromosuccinimide in acetonitrile to give mainly the corresponding 2-bromo-2-deoxy-α-glycopyranosides (4-21). The glycopyranosides (4-8 and16-21) from1 and3 have the α-d-manno configuration and those (10-15) from2 have the α-l-altro configuration. The yields are high from1, virtually quantitative from2, and moderate from3. Debromination of the 2-bromo-2-deoxy compounds with tributylstannane and a radical initiator gives the corresponding 2-deoxy-α-glycopyranosides (22-38) in quantitative yields. In particular, the branched-chain glycal2 reacts with alcohols to give exclusively the corresponding α-glycopyranosides (27-32) of cladinose in strikingly high overall yields. The stereoselectivity and regiospecificity of the bromination reaction are described. 1,3-Dibromo-5,5-dimethylhydantoin andN-bromoacetamide are also found to be useful for the reaction.     

Synthesis of 2- (and 6-) -dithian-2-yluracil nucleosides and their conversion into nucleoside derivatives

Addition of 2,2′-anhydro-[1-(3-O-acetyl-5-O-trityl-β-D-arabinofuranosyl)uracil] (1) to excess 2-litho-1,3-dithiane (2)in oxolane at ?78° gave 2-(1,3-dithian-2-yl)-1-(5-O-trityl-β-D-arabinofuranosyl)-4(1H)pyrimidinone (3), O²,2′-anhydro-5,6-di-hydro-6-(S)-(1,3-dithian-2-yl)-5′-O-trityluridine (4), and 2-(1,4-dihydroxybutyl)-1,3-dithiane (5) in yields of 15, 30, and 10% respectively. The structure of 3 was proved by its hydrolysis in acid to give 2-(1,3-dithian-2-yl)-4-pyrimidinone (6) and arabinose, and by desulfurization with Raney nickel to yield the known 2-methyl-1-(5-O-trityl-β-D-arabinofuranosyl)-4(1H)-pyrimidinone (7). Detritylation of 3 without glycosidic cleavage could only be effected by prior acetylation to 1-(2,3-di-O-acetyl-5-O-trityl-β-D-arabinofuranosyl)-2-(1,3-dithian-2-yl)-4(1H)-pyrimidinone (8) which, after treatment with acetic acid at room temperature for 65 h followed by the action of sodium methoxide gave 2-(1,3-dithian-2-yl)-1-β-D-arabinofuranosyl-4(1H)-pyrimidinone (10) in 45% yield. Detritylation of 4 in boiling acetic acid gave 5,6-dihydro-6-(S)-(1,3-dithian-2-yl)-1-β-D-arabinofuranosyluracil (12) and 3-[(S)-1-(1,3-dithian-2-yl)]propionamido-(1,2-dideoxy-β-D-arabinofurano)-[1,2-d]-2-oxazolidinone (13) in 10 and 90% yields, respectively. When 12 was kept in water or methanol for 7 days, quantitative conversion into 13 occurred. Acid hydrolysis of 12 afforded arabinose and 5,6-di-hydro-6-(1,3-dithian-2-yl)uracil (14), which was desulfurized with Raney nickel to the known 5,6-dihydro-6-methyluracil (15). Treatment of 13 with trifluoroacetic anhydride-pyridine yielded 77% of the cyano derivative 17. Similar dehydration of 3-(R)-1-methylpropionamido-(1,2-dideoxy-β-D-arabinofurano)-[1,2-d]-2-oxalidinone (18), obtained by desulfurization of 13, gave 60% of the nitrile 19. Hydrogenation of 19 over platinum oxide in acetic anhydride gave the acetamide derivative 20 in 95% yield. Nitrobenzoylation of 13 gave 3-[(S)-1-(1,3-dithian-2-yl)]cyanomethyl-3,5-di-O-p-nitrobenzoyl-(1,2-dideoxy-β-D-arabinofurano)-[1,2-d]-2-oxazolidinone (22), which was converted in 37% yield by treatment with methyl iodide in dimethyl sulfoxide into the aldehyde 24, characterized as the semicarbazone 25. The purification of 5 and its characterization as 2-(1,4-di-O-p-nitrobenzoylbutyl)-1,3-dithiane (27) is described.     

Solvent effects on the photochemical addition of acetone to 3,4,6-tri-O-acetyl-D-glucal

Irradiation of a solution of 3,4,6-tri-O-acetyl-D-glucal (1) in various mixtures of acetone (2) and isopropyl alcohol was investigated to elucidate solvent effects on the photochemical addition of 2 to 1. At high concentrations of acetone (2), 5,6,8-tri-O-acetyl-2,4:3,7-dianhydro-1-deoxy-2-C-methyl-D-glycero-D-ido-octitol (3) was obtained selectively. In mixtures containing less than 50% (v/v) of 2, irradiation gave mainly 5,6,8-tri-O-acetyl-3,7-anhydro-1,4-dideoxy-2-C-methyl-D-gluco-octitol (4). The effects of ethanol and other solvents were examined and the mechanism of the reaction is discussed.     

Synthesis of phenyl 2-acetamido-2-deoxy-3-O-α-l-fucopyranosyl-β-d-glucopyranoside and related compounds

The reaction of phenyl 2-acetamido-2-deoxy-4,6- O-(p-methoxybenzylidene)-β-d-glucopyranoside with 2,3,4-tri-O-benzyl-α-l-fucopyranosyl bromide under halide ion-catalyzed conditions proceeded readily, to give phenyl 2-acetamido-2-deoxy-4,6-O-(p-methoxybenzylidene)-3-O-(2,3,4-tri-O-benzyl-α-l-fucopyranosyl)-β-d-glucopyranoside (8). Mild treatment of 8 with acid, followed by hydrogenolysis, provided the disaccharide phenyl 2-acetamido-2-deoxy-3-O-α-l-fucopyranosyl-β-d-glucopyranoside. Starting from 6-(trifluoroacetamido)hexyl 2-acetamido-3,4,6-tri-O-acetyl-2-deoxy-β-d-glucopyranoside, the synthesis of 6-(trifluoroacetamido)hexyl 2-acetamido-2-deoxy-3-O-β-l-fucopyranosyl-β-d-glucopyranoside has been accomplished by a similar reaction-sequence. On acetolysis, methyl 2-acetamido-2-deoxy-3-O-α-l-fucopyranosyl-α-d-glucopyranoside gave 2-methyl-[4,6-di-O-acetyl-1,2-dideoxy-3-O-(2,3,4-tri-O-acetyl-α-l-fucopyranosyl)-α-d-glucopyrano]-[2, 1-d]-2-oxazoline as the major product.