The synthesis of methyl 4-O-(4-O-α-d-galactopyranosyl-β-d-galactopyranosyl)-β-d-glucopyranoside: The methyl β-glycoside of the trisaccharide related to Fabry's disease

As part of a program to synthesize the ceramide trisaccharide (1) related to Fabry's disease, methyl 4-O-(4-O-α-$\text{d}$-galactopyranosyl-β-$\text{d}$-galactopyranosyl)-β-$\text{d}$-glucopyranoside (12) was prepared. Methyl β-lactoside (2) was converted into methyl 4-O-(4,6-O-benzylidene-β-$\text{d}$-galactopyranosyl)-β-$\text{d}$-glucopyranoside (4). Methyl 2,3,6-tri-O-benzoyl-4-O-(2,3,6-tri-O-benzoyl-β-$\text{d}$-galactopyranosyl)-β-$\text{d}$-glucopyranoside (7) was synthesized from 4 through the intermediates methyl 2,3,6-tri-O-benzoyl-4-O-(4,6-O-benzylidene-2,3-di-O-benzoyl-β-$\text{d}$-galactopyranosyl)-β-$\text{d}$-glucopyranoside (5) and methyl 2,3,6-tri-O-benzoyl-4-O-(2,3-di-O-benzoyl-β-$\text{d}$-galactopyranosyl)-β-$\text{d}$-glucopyranoside (6). The halide-catalyzed condensation of 7 with 2,3,4,6-tetra-O-benzyl-$\text{d}$-galactopyranosyl bromide (8) gave methyl 2,3,6-tri-O-benzoyl-4-O-[2,3,6-tri-O-benzoyl-4-O-(2,3,4,6-tetra-O-benzyl-α-$\text{d}$-galactopyranosyl)- β-$\text{d}$-galactopyranosyl]-β-$\text{d}$-glucopyranoside (10). Stepwise deprotection of 10 led to 12, the methyl β-glycoside of the trisaccharide related to Fabry's disease.     

3-deoxy-2,5-DI-O-p-nitrobenzoyl-α-D-threo-pentofuranosyl bromide,a starting material for the synthesis of nucleosides

Hydrogenation (Raney nickel) of methyl 2,3-anhydro-α- and β-D-lyxo-furanoside (3 and 12) for 12 h at $\text{60}\text{60}$ lb.in.-2 afforded methyl 3-deoxy-α- and β-D-threo pentofuranoside (4 and 13). These were p-nitrobenzoylated to give the 2,5-di-p-nitrobenzoates (5b and 14b) which, on treatment with hydrogen bromide in acetyl bromide—acetic acid—dichloromethane, afforded the title compound (6b). The structure of compound 4 was established by conversion into the previously prepared 2,5-dibenzoate 5a of known structure, and the anomeric configuration of 6b was established by comparison of its optical rotation and the signals of its anomeric proton with those of methyl 3-deoxy-D-threo-pentofuranosides.     

The stepwise synthesis of an aldopentaouronic acid derivative related to branched (4-O-methylglucurono)xylans

Benzylation of methyl 2,3-anhydro-4-O-[2-O-benzyl-3,4-di-O-(β-D-xylop yranosyl]-β-D-xylopyranosyl]-β-D-ribopyranoside (1) afforded the crystalline. fully benzylated tetrasaccharide derivative 2. The octa-O-benzyl derivative 3, having only HO-2 unsubstituted, obtained by treatment of 2 with benzyl alcoholate anion in benzyl alcohol, was allowed to react in dichloromethane with methyl 2,3-di-O-benzyl- 1-chloro-1-deoxy-4-O-methy]-α,β-glucopyranuronate in the presence of silver perchlorate and triethylamine to give the branched, 4-O-methyl-α-D-glucuronic acid-containing pentasaccharide derivative 4a as the major product. Subsequent debenzylation afforded the aldopentaouronic acid derivative 5a, which contains all the basic structural features of branched, hardwood (4-O-methylglucurono)xylans. The structure of 5a was confirmed by analysis of its ¹³C-n.m.r. spectrum and the mass-spectral fragmentation pattern of the corresponding fully methylated derivative 6a.     

The stepwise synthesis of a methyl β-xylotetraoside related to branched xylans

3,4-Di-O-acetyl-2-O-benzyl-α-d-xylopyranosyl bromide (1) reacts with methyl 2,3-anhydro-α-d-ribopyranoside (2) to afford, in high yield, methyl 2,3-anhydro-4-O- (3,4-di-O-acetyl-2-O-benzyl-β-d-xylopyranosyl)-β-d-ribopyranoside (3). Deacetylation of 3 gave 4, which reacted with 2,3,4-tri-O-acetyl-α-d-xylopyranosyl bromide to give the branched tetrasaccharide derivative 5, which, in turn, was converted by a series or conventional reactions into methyl 4-O-[3,4-di-O-(β-d-xylopyranosyl)-β-d- xylopyranosyl]-β-d-xylopyranoside. The reaction of 1 with its hydrolysis product gave 3,4-di-O-acetyl-2-O-benzyl-α-d-xylopyranosyl 3,4-di-O-acetyl-2-O-benzyl-β-d-xylopyranoside, which was also isolated after the reaction of 1 with 2.     

Studies on dextranases. 3. Insolubilization of a bacterial dextranase

Ammonium hydroxide treatment of 1,6:2,3-dianhydro-4-O-benzyl-β-D-mannopyranose, followed by acetylation, gave 2-acetamido-3-O-acetyl-1,6-anhydro-4-O-benzyl-2-deoxy-β-D-glucopyranose which was catalytically reduced to give 2-acetamido-3-O-acetyl-1,6-anhydro-2-deoxy-β-D-glucopyranose (6), the starting material for the synthesis of (1→4)-linked disaccharides bearing a 2-acetamido-2-deoxy-D-glucopyranose reducing residue. Selective benzylation of 2-acetamido-1,6-anhydro-2-deoxy-β-D-glucopyranose gave a mixture of the 3,4-di-O-benzyl derivative and the two mono-O-benzyl derivatives, the 4-O-benzyl being preponderant. The latter derivative was acetylated, to give a compound identical with that just described. For the purpose of comparison, 2-acetamido-4-O-acetyl-1,6-anhydro-2-deoxy-β-D-glucopyranose has been prepared by selective acetylation of 2-acetamido-1,6-anhydro-2-deoxy-β-D-glucopyranose.Condensation between 2,3,4,6-tetra-O-acetyl-α-D-glucopyranosyl bromide and 6 gave, after acetolysis of the anhydro ring, the peracetylated derivative (17) of 2-acetamido-2-deoxy-4-O-β-D-glucopyranosyl-α-D-glucopyranose. A condensation of 6 with 3,4,6-tri-O-acetyl-2-deoxy-2-diphenoxyphosphorylamino-α-D-glucopyranosyl bromide likewise gave, after catalytic hydrogenation, acetylation, and acetolysis, the peracylated derivative (21) of di-N-acetylchitobiose.     

Synthesis of 3,4-anhydro-1-deoxy-3-C-methyl-d-hexulose derivatives

Epoxidation of (E)-1,3,4-trideoxy-5,6-O-isopropylidene-3-C-methyl-d-glycero-hex-3-enulose by alkaline hydrogen peroxide gave a mixture of 3,4-anhydro-1-deoxy-5,6O-isopropylidene-3-C-methyl-d-arabino- (2) and -d-xylo-hexulose (3) that was resolved by chromatography. From the reaction of 2 with 3-chloroperbenzoic acid, the Baeyer-Villiger rearrangement product (2R)-2-O-acetyl-2,3-anhydro-1-deoxy-4,5-O-isopropylidene-d-eythro-pentulose hydrate was isolated. The structures and configurations of the above products were established on the basis of chemical transformations and anlytical and spectroscopic data.     

Isolation of 2,5-anhydro-1,3-O-isopropylidene-6-O-trityl-D-glucitol and conformations of its 4-O-substituted and deprotected,acylated derivatives

Acidic dehydration of D-mannitol (1) gave a mixture of anhydrides (2) that was isopropylidenated and subsequently tritylated. A single component crystallized from the resulting mixture and was shown to be the novel 2,5-anhydro-1,3-O-isopropylidene-6-O-trityl-D-glucitol (4) by chemical and physical analysis and by comparison of its deprotected, dibenzoylated derivative (10) with authentic 2,5-anhydro-1,6-di-O-benzoyl-D-glucitol. Acid hydrolysis of 4 afforded pure 2,5-anhydro-D-glucitol (9) in better yield than by the previously reported route. The 4-O-acetyl (5), 4-O-chloro-acetyl (6), 4-O-methyl (7), and 4-O-(methylsulfonyl) (8) derivatives of 4, the tetra-O-acetyl (11) derivative of 9, and the 3,4-di-O-acetyl (12) derivative of 10, have been prepared and spectrally characterized. Complete proton-n.m.r. analysis yields first-order coupling constants that indicate the E₁ (D) conformation for the tetrahydrofuran ring and the chair conformation for the 1,3-dioxane ring of 4-2-8. Obtainable coupling constants suggest that 11 and 12 exist in the ^oE and/or ^oT₁, conformations.     

The synthesis of the α-d-anomers of “homonucleosides”: derivatives of 2,5-anhydro-d-altritol

Reaction of 2,3,5-tri-O-benzyl-d-ribofuranosyl bromide with mercuric cyanide afforded an anomeric mixture of cyanides (3) and 1,4-anhydro-2,3,5-tri-O-benzyl-d-erythro-pent-1-enitol (6). Reduction of 3 with lithium aluminum hydride gave a pair of epimeric amines (4 and 5), which were separated by chromatography and characterized by conversion into the known 2,5-anhydro-3,4,6-tri-O-benzyl-1-deoxy-1-ureido-d-allitol (7) and its epimer, 2,5-anhydro-3,4,6-tri-O-benzyl-1-deoxy-1-ureido-d-altritol (8). Compound 8 and its precursor were used for the synthesis of various “α-homonucleosides”.     

Reactions of the antitumor agent carminic acid and derivatives with DNA

The antitumor agent carminic acid 1a does not bind to DNA but nicks it slowly, more rapidly when reduced in situ, and still more rapidly when prereduced at the quinone moiety. The nicking process requires oxygen and is selectively inhibited by (i) superoxide dismutase, (ii) catalase, and (iii) free radical scavengers indicating the involvement of $\text{O}{}_2{}^{\mathrm{<mtext>?</mtext>}}\text{, H}{}_2\text{O}{}_2$, and OH^., respectively. The intermediacy of OH^. was supported by spin trapping with N-t-butyl-α-phenylnitrone and epr of the radical produced via the carminic acid semiquinone. The single strand scission of DNA by carminic acid requires two adjacent hydroquinone moieties in the chromophore since reduced methyl tetra-O-methylcarminate 1b is without effect although it binds weakly to DNA. Polarographic redox potentials for the reversible (2e, 2H⁺) reduction of 1a and 1b are ?0.736 ± 0.003 V and ?0.56 ± 0.010 V against SCE, respectively. The fact that daunorubicin and adriamycin produce more extensive DNA strand scission than carminic acid under comparable conditions of prereduction and on a molar basis is largely attributed to the assistance of intercalative binding afforded in the case of the anthracyclines.     

Nitrous acid deamination of conformationally inverted aminodeoxyhexopyranoses

Nitrous acid deamination of 2-amino-1,6-anhydro-2-deoxy-β-D-glucopyranose (1) in the presence of weakly acidic, cation-exchange resin gave 1,6:2,3-dianhydro-β-D-mannopyranose (3) and 2,6-anhydro-D-mannose (6), characterized, respectively, as the 4-acetate of 3 and the per-O-acetylated reduction product of 6, namely 2,3,4,6- tetra-O-acetyl-1,5-anhydro-D-mannitol, obtained in the ratio of 7:13. Comparative deaminatior of the 4-O-benzyl derivative of 1 led to similar qualitative results. Deamination of 3-amino-1,6-anhydro-3-deoxy-β-D-glucopyranose gave 1,6:2,3- and 1,6:3,4-dianhydro-β-D-allopyranose (13 and 16), characterized as the corresponding acetates, obtained in the ratio of 31:69, as well as the corresponding p-toluenesulfonates. Deamination of 4-amino-1,6-anhydro-4-deoxy-β-D-glucopyranose and of its 2-O-benzyl derivative gave the corresponding 1,6:3,4-D-galacto dianhydrides as the only detectable products. 2,5-Anhydro-D-glucose, characterized as the 1,3,4,6-tetra-O- acetyl derivative of the corresponding anhydropolyol, was obtained in 39% yield from the same deamination reaction performed on 2-amino-1,6-anhydro-2-deoxy-β-D- mannopyranose (24). In 90% acetic acid, the nitrous acid deamination of 24, followed by per-O-acetylation, gave only 1,3-4-tri-O-acetyl-2,5-anhydro-α-D-glucoseptanose. In the case of 1,6-anhydro-3,4-dideoxy-3,4-epimino-β-D-altropyranose, only the corresponding glycosene was formed, namely, 1,6-anhydro-3,4-dideoxy-β-D-threo--hex-3-enopyranose.     

Synthesis of 8-(hydroxyalkyl)adenines

Treatment of methyl 4,6-O-benzylidene-2-O-p-tolylsulfonyl-α-D-ribo-hexopyranosid-3-ulose (1) with triethylamine-methanol at reflux temperature yields methyl 2,3-anhydro-4,6-O-benzylidene-3-methoxy-α-D-allopyranoside (2), a derivative (3) of 3-hydroxy-2-(hydroxymethyl)-4H-pyran-4-one, and methyl 4,6-O-benzylidene-α-D-ribo-hexopyranosid-3-ulose dimethyl acetal (4). The reaction of methyl 4,6-O benzylidene-3-O-p-tolylsulfonyl-α-D-arabino-hexopyranosid-2-ulose (12) with triethylamine-methanol afforded methyl 4,6-O-benzylidene-α-D-ribo-hexopyranosid-2-ulose dimethyl acetal (19) and methyl 2,3-anhydro-4,6-O-benzylidene-2-methoxy-α-D-allopyranoside (20); from the reaction of the β-D anomer (13) of 12, methyl 4,6-O-benzylidene-β-D-ribo-hexopyranosid-2-ulose dimethyl acetal (21) was isolated. Syntheses of the α-keto toluene-p-sulfonates 12 and 13 are described. Mechanisms for the formation of the compounds isolated from the reactions with triethylamine-methanol are proposed.     

Photochemical addition of 2-propanol and of acetone to 2-acetoxy-3,4,6-tri-O-acetyl-D-glucal

Irradiation of a solution of 2-acetoxy-3,4,6-tri-O-acetyl-D-glucal (1) in 1:200 acetone-2-propanol with a high-pressure mercury-lamp gave 4,5,6,8-tetra-O-acetyl-3,7-anhydro-1-deoxy-2-C-methyl-D-glycero-D-gulo-octitol (2) (51.2%), -D-glycero-D-ido-octitol (3) (16.2%), and-D-glycero-D- galacto-octitol (4) (21.0%). The irradiation of 1 in 1:1 acetone-2-propanol gave 5,6,8-tri-O-acetyl-3,7-anhydro-1-deoxy-4-C-(1-hydroxy-1-methylethyl)-2-C-methyl-D-glycero-D-(gluco or manno, etc.)-octitol 2,4,4¹-orthoacetate (17%) and a 2:1:1 mixture of 2, 3, and 4 (64%). Moreover, the irradiation of 1 in 1:9 acetone-tert-butyl alcohol gave 2 (15%), 3 (9%), 4 (7%), and (4S)-4,5,6,8-tetra-O-acetyl-2,4:3,7-dianhydro-1-deoxy-2-C-methyl-D-gluco-octos-4-ulose (14%).     

1-trans-Parinaroyl phospholipids: Synthesis and fast atom bombardment/electron impact mass spectrometric characterization

1-trans-Parinaroyl-2-linoleoyl-sn-glycero-3-phosphocholine (1–18:4-2-18:2-GPC) was synthesized from lecithin and parinaric acid by the following route: $\text{diacyl-GPC}\text{→}\text{GPC}\text{→ 1,2-}\text{di}\text{-18:4-}\text{GPC}\text{(}\text{I}\text{) → 1–18:4-}\text{GPC}\text{(}\text{II}\text{) → 1–18:4-2-18:2-}\text{GPC}\text{(}\text{III}\text{)}$. The identity of I, II and III was established by fast atom bombardment (FAB) mass spectrometry of the intact molecules as well as electron impact (E1) mass spectrometry of the corresponding O-TMS derivatives obtained after phospholipase C treatment and silylation. Temperature dependent phase transition of phospholipid liposomes was performed in the presence of III.     

Synthesis of 2-deoxy-2-fluorohexoses by fluorination of glycals in aqueous media

1,5-Anhydro-2-deoxy-d-arabino- (d-glucal), 1,5-anhydro-2-deoxy-d-lyxo- (d-galactal), and 3,4,6-tri-O-acetyl-1,5-anhydro-2-deoxy-d-lyxo-hex-1-enitol (3,4,6-tri-O-acetyl-d-galactal) (3) were fluorinated in water and organic solvent-water with molecular fluorine and, for ¹⁸F-labelled compounds, with [¹⁸F]fluorine. Chemical yields of 40 and 10% were obtained for 2-deoxy-2-fluoro-d-glucose and 2-deoxy-2-fluoro-d-mannose, respectively, and 35 and 5% for 2-deoxy-2-fluoro-d-galactose (12) and 2-deoxy-2-fluoro-d-talose (13), respectively. In the fluorination of 3, the chemical yields of 12 and 13 were 38 and 6%, respectively. An l.c. separation of 2-deoxy-2-fluoro-d-hexoses is described.     

Chlorophyll-protein complexes of a Codium species,including a light-harvesting siphonaxanthin-Chlorophylla ab-protein complex,an evolutionary relic of some Chlorophyta

Eight chlorophyll-protein complexes were isolated from thylakoid membranes of a Codium species, a marine green alga, by mild SDS-polyacrylamide gel electrophoresis. CP 1a¹, CP 1a², CP 1a³ and CP 1a⁴ were partially dissociated Photosystem (PS) I complexes, which in addition to the core reaction centre complex, CP 1, possessed PS I light-harvesting complexes containing chlorophyll (Chl) a, Chl b and siphonaxanthin. LHCP¹ and LHCP³ are orange-brown green chlorophyll $\text{a}\text{b-}\text{proteins}$ ($\text{Chl}\text{a}\text{Chl}\text{b}$ ratios of 0.66) that contain siphonaxanthin and its esterified form, siphonein. CP a and CP 1, the core reaction centre complexes of PS II and PS I, respectively, had similar spectral properties to those isolated from other algae or higher plants. These P-680- or P-700-Chl a-proteins are universally distributed among algae and terrestrial plants; they appear to be highly conserved and have undergone little evolutionary adaptation. Siphonaxanthin and siphonein which are present in the Codium light-harvesting complexes of PS II and PS I are responsible for enhanced absorption in the green region (518 and 538 nm). Efficient energy transfer from both xanthophylls and Chl b to only Chl a in Codium light-harvesting complexes, which have identical fluorescence emission spectra at 77 K to those of the lutein-Chl $\text{a}\text{b-}\text{proteins}$ ($\text{Chl}\text{a}\text{Chl}\text{b}$ ratios of 1.2) of most green algae and all higher plants, proved that the molecular arrangement of these light-harvesting pigments was maintained in the isolated Codium complexes. The siphonaxanthin-Chl $\text{a}\text{b-}\text{proteins}$ allow enhanced absorption of blue-green and green light, the predominant light available in deep ocean waters or shaded subtidal marine habitats. Since there is a variable distribution of lutein, siphonaxanthin and siphonein in marine green algae and siphonaxanthin is found in very ancient algae, these novel siphonein-siphonaxanthin-Chl $\text{a}\text{b-}\text{proteins}$ may be ancient light-harvesting complexes which were evolved in deep water algae.     

Ring-opening reactions of sucrose epoxides: Synthesis of 4′-derivatives of sucrose

The 2,1′-O-isopropylidene derivative (1) of 3-O-acetyl-4,6-O-isopropylidene-α-d-glucopyranosyl 6-O-acetyl-3,4-anhydro-β-d-lyxo-hexulofuranoside and 2,3,4-tri-O-acetyl-6-O-trityl-α-d-glucopyranosyl 3,4-anhydro-1,6-di-O-trityl-β-d-lyxo-hexulofuranoside have been synthesised and 1 has been converted into 2,3,4,6-tetra-O-acetyl-α-d-glucopyranosyl 1,6-di-O-acetyl-3,4-anhydro-β-d-lyxo-hexulofuranoside (2). The S_N2 reactions of 2 with azide and chloride nucleophiles gave the corresponding 2,3,4,6-tetra-O-acetyl-α-d-glucopyranosyl 1,3,6-tri-O-acetyl-4-azido-4-deoxy-β-d-fructofuranoside (6) and 2,3,4,6-tetra-O-acetyl-α-d-glucopyranosyl 1,3,6-tri-O-acetyl-4-chloro-4-deoxy-β-d-fructofuranoside (8), respectively. The azide 6 was catalytically hydrogenated and the resulting amine was isolated as 2,3,4,6-tetra-O-acetyl-α-d-glucopyranosyl 4-acetamido-1,3,6-tri-O-acetyl-4-deoxy-β-d-fructofuranoside. Treatment of 5 with hydrogen bromide in glacial acetic acid followed by conventional acetylation gave 2,3,4,6-tetra-O-acetyl-α-d-glucopyranosyl 1,3,6-tri-O-acetyl-4-bromo-4-deoxy-β-d-fructofuranoside. Similar S_N2 reactions with 2,3,4,6-tetra-O-acetyl-α-d-glucopyranosyl 1,6-di-O-acetyl-3,4-anhydro-β-d-ribo-hexulofuranoside (12) resulted in a number of 4′-derivatives of α-d-glucopyranosyl β-d-sorbofuranoside. The regiospecific nucleophilic substitution at position 4′ in 2 and 12 has been explained on the basis of steric and polar factors.