Michael Heidelberger as a Carbohydrate Chemist

The deoxyaldaric acids corresponding in structure to the 3-deoxy-2-C-(hydroxymethyl)aldonic (isosaccharinic) acids have been identified as products of treatment of various carbohydrates with alkali and oxygen-alkali. The structures of the acids were determined from the mass spectra of their Me₃Si derivatives on the basis of previously known, specific fragmentation reactions. The g.l.c.-m.s. technique was used, and g.l.c. retention data are given. The identified species are 2-deoxy-3-C-(hydroxymethyl)tetraric, 3-deoxy-2-C-hydroxymethyl-erythro-pentaric, 3-deoxy-2-C-hydroxymethyl-threo-pentaric, 2-methyltartronic, 2-(2-hydroxyethyl)tartronic, and 2-(2,3-dihydroxypropyl)tartronic acids. Their formation from 4-O-substituted uronic and ulosonic acids is briefly discussed.     

Synthesis of branched-chain,pyrrolidino-sugar derivatives related to apiose

3-C-(Acetamidomethyl)-1,2-O-isopropylidene-β-l-threofuranose (4) and the 3-acetate (5) have been prepared in high yields from mono-O-isopropylidene-d-apiose [3-C-(hydroxymethyl)-1,2-O-isopropylidene-β-l-threofuranose] (1). Acid-catalyzed methanolysis of 4 caused migration of the isopropylidene group and the formation of methyl 4-acetamido-4-deoxy-3-C-(hydroxymethyl)-2,3-O-isopropylidene-β-d-erythrofuranoside (8) in 25% yield. The major product (45%) from the acetolysis of 4 was also a pyrrolidine derivative, namely, 4-acetamido-3-C-(acetoxymethyl)-1-O-acetyl-4-deoxy-2,3-O-isopropylidene-β-d-erythrofuranose (10). Acetolysis of 5 removed the isopropylidene group and gave four acetylated pyrrolidines (isomeric at C-1 and C-2). Conditions which resulted in minimal epimerization at C-2 were established, and the major isomers 12 and 13 were isolated in reasonable yields. ¹H- and ¹³C-n.m.r. data for equilibrium solutions of the pyrrolidines, and for intermediates 1-5, are given.     

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.     

Sugar-related hydroxy acids from Phaseolus and trifolium species

-Hydroxy acids isolated from leaves of French bean (Phaseolus vulgaris) and clover (Trifolium incarnatum) were analysed by GLC as trimethylsilyl derivatives and identified by MS. Large amounts of a 2-C-methyltetronic acid and appreciable amounts of gluconic acid and of a 2-C-(hydroxymethyl)pentonic acid were found from French bean. Glyceric acid was the predominant acid from clover but the presence of several other acids, e.g. threonic and malic acids, was also demonstrated.     

Silylmethylene radical cyclization. A stereoselective approach to branched sugars

Ethyl 6-O-benzyl-2,3-dideoxy-α-d-erythro-hex-2-enopyranoside (2) was converted, in three steps and in 73% overall yield, into ethyl 6-O-benzyl-2,3-dideoxy-3-C-(hydroxymethyl)-α-d-ribo-hex-2-enopyranoside. This transformation involved silylation of 2 with (bromomethyl)chlorodimethylsilane and application of the Nishiyama-Stork radical cyclisation, followed by Tamao oxidation of the sila cycle. Ethyl 6-O-benzyl-2,3-dideoxy-α-d-threo-hex-2-enopyranoside and benzyl 2,6-di-O-benzyl-α-l-threo-hex-4-enopyranoside were similarly transformed into, respectively, ethyl 6-O-benzyl-2,3-dideoxy-3-C-(hydroxymethyl)-α-d-lyxo-hex-2-enopyranoside (50%), and benzyl 2,6-di-O-benzyl-4-deoxy-4-C-(hydroxymethyl)-β-d-galactopyranoside (71%).     

Non-oxidative and oxidative degradation of d-galacturonic acid with alkali

Degradation products from non-oxidative and oxidative treatment of d-galacturonic acid with alkali have been analysed by g.l.c.-m.s.; 13 hydroxy monocarboxylic acids and 26 dicarboxylic acids were identified in addition to several isomerisation products. In the absence of oxygen, the main degradation products were 3-deoxy-lyxo-hexaric, 3-deoxy-xylo-hexaric, malic, tartonic, C-methyltartronic, lactic, and 3-deoxytetronic acids. In the presence of oxygen, arabinaric, threaric, malic, tartronic, and glycolic acids were formed in large proportions. The routes of formation for most of the compounds are outlined.     

The synthesis of P1-2-acetamido-4-O-(2-acetamido-2-deoxy-β-d-glucopyranosyl)-2-deoxy-α-d-glucopyranosyl P2-dolichyl pyrophosphate, (P1-di-N-acetyl-α-chitobiosyl P2-dolichyl pyrophosphate)

2-Acetamido-4-O-(2-acetamido-2-deoxy-β-d-glucopyranosyl)-2-deoxy-α-d-glucopyranosyl phosphate, pure according to thin-layer and gas—liquid chromatography, optical rotation, and treatment with alkaline phosphatase and 2-acetamido-2-deoxy-β-d-glucosidase, was prepared by treatment of 2-methyl-[4-O-(2-acetamido-3,4,6-tri-O-acetyl-2-deoxy-β-d-glucopyranosyl)-3,6-di-O-acetyl-1,2-dideoxy-α-d-glucopyrano]-[2,1-d]-2-oxazoline with dibenzyl phosphate, followed by the removal of the benzyl groups by catalytic hydrogenolysis, and O-deacetylation. In contrast, a sample prepared by the phosphoric acid procedure was shown to consist mainly of the β anomer. 2-Acetamido-4-O-(2-acetamido-3,4,6-tri-O-acetyl-2-deoxy-β-d-glucopyranosyl)-3,6-di-O-acetyl-2-deoxy-α-d-glucopyranosyl phosphate was treated wit P¹-diphenyl P²-dolichyl pyrophosphate to give a fully acetylated pyrophosphoric diester, which was O-deacetylated to give P¹-2-acetamido-4-O-(2-acetamido-2-deoxy-β-d-glucopyranosyl)-2-deoxy-α-d-glucopyranosyl P²-dolichyl pyrophosphate. This compound could be separated from the β anomer by t.l.c., and its behavior under dilute acid and alkaline conditions was investigated.     

Characterization of alkaline-degradation products of some 3,4-di- and 3,4,6-tri-methyl ethers of hexoses by G.L.C.-mass spectrometry of O-trimethylsilyl derivatives

G.l.c.-mass spectrometry has been used to provide information on the O-trimethylsilyl derivatives of the products of alkaline degradation of 3,4-di- and 3,4,6-tri-O-methyl-D-glucose, and 3,4,6-tri-O-methyl-D-galactose. During reaction with sodium hydroxide-sodium borohydride mixtures, reduction occurs more rapidly than β-elimination and the only detectable products were the corresponding alditols and the epimeric 3-deoxyalditols. Extended reaction with sodium hydroxide alone, followed by treatment with sodium borohydride, gives mixtures of aldonic acids including the epimeric 3-deoxy-4-O-methylaldonic acids (metasaccharinic acids), 3-deoxyaldonic acids (with loss of the 4-O-methyl substituent), and 3,4-dideoxy-aldonic acids. Possible reaction-pathways are discussed.     

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.     

Photochemical addition of 1,3-dioxolane and of 2-propanol to 1,2,4,6-tetra-O-acetyl-3-deoxy-α- and -β-D-erythro-hex-2-enopyranose

Photoirradiation of a solution of 1,2,4,6-tetra-O-acetyl-3-deoxy-β-D-erythro-hex-2-enopyranose (1) in 1:50 acetone-1,3-dioxolane with a high-pressure mercury-lamp, followed by chromatographic separation, gave 1,2,4,6-tetra-O-acetyl-3-deoxy-3-C-(1,3-dioxolan-2-yl)-β-D-glucopyranose (3) (44%) and-mannopyranose (4) (35%). Similar treatment of the α anomer (2) of 1 afforded 1,2,4,6-tetra-O-acetyl-3-deoxy-3-C-(1,3-dioxolan-2-yl)-α-D-glucopyranose (5) (38%), -mannopyranose (6) (31%), and -allopyranose (7) (21%).On the other hand, irradiation of 2 in 1:100 acetone-2-propanol gave 1,2,4,6-tetra-O-acetyl-3-deoxy-3-C-(1-hydroxy-1-methylethyl)-α-D-mannopyranose (8) (76%). Moreover, irradiation of 2 in 1:1 acetone-2-propanol yielded 1,4,6-tri-O-acetyl-3-deoxy-2,3-di-C-(1-hydroxy-1-methylethyl)-α-D-gluco- or -manno-pyranose 2,2¹,3¹-orthoacetate (10) (15%), in addition to 8 (44%).     

Nitrous acid deamination of methylated amino-oligosaccharide glycosides

G.l.c.-mass spectrometry has been used to characterize the products of N-deacetylation-nitrous acid deamination of per-O-methylated derivatives (8–11) of methyl 2-acetamido-2-deoxy-3-O-β-D-galactopyranosyl-α-D-glucopyranoside(1), methyl (2) and benzyl (3) 2-acetamido-2-deoxy-4-O-β-D-galactopyranosyl-β-D-glucopyranosides, and methyl 2-acetamido-2-deoxy-6-O-β-D-galactopyranosyl-α-D-glucopyranoside (4). 2,5-Anhydrohexoses have been converted into alditol trideuteriomethyl ethers, alditol acetates, and aldononitriles. The importance of side reactions that lead to the formation of 2-deoxy-2-C-formylpentofuranosides is discussed.     

Reaction pathways of glucose oxidation by ozone under acidic conditions

The ozonation of d-glucose-1-¹³C, 2-¹³C, and 6-¹³C was carried out at pH 2.5 in a semi-batch reactor at room temperature. The products present in the liquid phase were analyzed by GC-MS, HPAEC-PAD, and ¹³C NMR spectroscopy. Common oxidation products of glucose have also been submitted to identical ozonation conditions. For the first time, a pentaric acid was identified and its formation quantitatively correlated to the loss of C-6 of glucose in the form of carbon dioxide. Potential mechanisms for the formation of this pentaric acid are discussed. The well-accepted pathway involving the anomeric position in glucose, gluconic acid, arabinose, and carbon dioxide is reinvestigated. The origin of small molecules such as tartaric, erythronic, and oxalic acids is clarified. Finally, new reaction pathways and tentative mechanisms consistent with the formation of ketoaldonic acids and smaller acids are proposed.     

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.     

Synthesis of an -quinovose-containing disaccharide

The synthesis of a versatile -rhamnose monosaccharide synthon is described. This synthon is used in the synthesis of a disaccharide containing the rare sugar, 6-deoxy- -glucose, linked to the 3-C-hydroxymethyl group of methyl 2,3-O-isopropylidene 3-C-(hydroxymethyl)-β- -erythrofuranoside.     

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).     

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.     

Équilibres conformationnels de glucides au niveau de liaisons σ SP-SP: Partie V. Dérivés 2,3,-O-isopropylidène de pyranosides hybrides sp en C-4. Comparaison avec leurs analogues saturés

The conformation in solution of derivatives of methyl hexopyranosides has been studied by n.m.r. The esters of methyl 2,3-O-isopropylidene-α-D-manno- and -talopyranosides as well as their 4-deoxy-4-C-methyl analog having a manno configuration exist mainly in a flattened (^4,0F) chair conformation (⁴C₁). The presence in the talo epimer of the 4-deoxy-4-C-methyl analog of the bulky methyl group on the endo side of the bicyclic system results in a skew form (³S₁). The methyl 4-deoxy-2,3-O-isopropylidene-4-C-methylene-α-D-lyxo-hexopyranosides monosubstituted at C-4′ adopt, in solution, a conformation close to ³S₁, whichever their configuration (cis or trans) at the double bond, as indicated by their allylic coupling constants.     

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.     

Configurational assignments of C-nitromethyl-C-hydroxy branched-chain carbohydrate derivatives by use of a europium shift-reagent in 1 H-N.M.R. spectroscopy

Configurational assignments for the tertiary alcoholic centers of four branched-chain 3-C-nitromethylglycopyranosides, namely, methyl 2-benzamido-4,6-O-benzylidene-2-deoxy-3-C-nitromethyl-α-D-allopyranoside (1), benzyl 2-acetamido-4,6-O-benzylidene-2-deoxy-3-C-nitromethyl-α-D-glucopyranoside (4), benzyl 2-acetamido-4,6-O-benzylidene-2-deoxy-3-C-nitromethyl-α-D-allopyranoside (5), and methyl 4,6-O-benzylidene-3-C-nitromethyl-2-O-p-tolylsulfonyl-α-D-glucopyranoside (8), were made on the basis of the downfield chemical shifts of their identifiable protons per molar equivalent of added Eu(fod)₃, as compared with those of model compounds, of known configuration, having a close structural relationship. In some cases, the assignments were corroborated by the position of the acetyl resonances in the unshifted 60-MHz p.m.r. spectra of the corresponding O-acetyl derivatives.     

A convenient synthesis of 2-deoxy-2-[(R)-1-hydroxytetradecanamido]-3-O-[(R)-3-hydroxytetradecanoyl]-α-d-glucopyranose 1-phosphate (lipid X)

The crystalline tris(hydroxymethyl)aminomethane (“Tris”) salt of 2-deoxy-2-[(R)-3-hydroxytetradecanamido]-3-O-[(R)-3-hydroxytetradecanoyl]-α-d-glucopyranose 1-phosphate (lipid X) has been synthesised from 2-amino-2-deoxy-d-glucose hydrochloride in five steps in ∼ 50% overall yield. The key step was 1-O-(dibenzyl) phosphorylation of 4,6-O-benzylidene-2-[(R)-3-benzyloxytetradecanamido]-2-deoxy-d-glucopyranose, catalysed by butyl-lithium. The product was then 3-(R)-3-benzyloxytetradecanoylated, and the benzyl and benzylidene groups were removed by catalytic hydrogenation.