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A four-step procedure for homologation of methyl α- d - manno furanoside and α- d - manno pyranoside was examined. The reactions consisted in (i) oxidation of the terminal hydroxymethyl group in a protected sugar derivative to an aldehyde; (ii) reaction with allyloxymethylmagnesium chloride (or (phenyldimethyl)silylmethyl–magnesium chloride); (iii) protection of the newly formed secondary alcohol group; (iv) deprotection of the terminal CH 2 OR (or oxidation of the CH 2 SiMe 2 Ph) group. From methyl α- d -mannosides, stereoisomeric d α d and l α d methyl heptosides and from them, methyl octosides of d - threo - and l - erythro -α- d - manno configuration were obtained.

Three O -isopropylidene group-protected pentose aldehydes (methyl 2,3- O -isopropylidene-β- d - ribo -pentodialdo-1,4-furanoside ( 1 ), methyl 2,3- O -isopropylidene-α- d - lyxo -pentodialdo-1,4-furanoside ( 2 ), and 3- O -benzyl-1,2- O -isopropylidene-α- d - xylo -pentodialdo-1,4-furanose ( 3 )) were treated at −30 °C with lithium diisopropylamide (LDA) and the mixtures obtained were reduced with LiAlH 4 . The products, obtained in moderate yields, proved that deacetonation occurred followed by aldol reactions between aldehydes 1 – 3 and acetone.

Methyl β-d-glucopyranoside reacted with a 4-molar excess of the Mitsunobu reagents (triphenylphosphine–diethyl azodicarboxylate–benzoic acid) under Weinges et al. [Carbohydr. Res., 164 (1987) 453–458] conditions to furnish four differently benzoylated methyl β-d-allopyranosides in a very good overall yield. The same reaction applied to methyl α-d-glucopyranoside yielded allosides in a low yield and nine other sugar products. These results give an insight into the course of the Mitsunobu esterification–inversion reaction.

Synthesis of the title trisaccharide was accomplished by sugar chain extension starting from the non-reducing terminus: coupling of Glc p NAc with ld -Hep p , then adding Glc p -OAll. An alternative route started from the reducing end: coupling of ld -Hep p with Glc p -OAll, then addition of Glc p NAc. In the synthesis of the title disaccharide a modification of the first approach was employed. The allyl glycosides were coupled with cysteamine, activated with thiophosgene and conjugated to bovine serum albumin (BSA). The neoglycoconjugates obtained were used in immunochemical studies of monoclonal and polyclonal antibodies directed against Escherichia coli K-12 lipopolysaccharide.

From suitably protected methyl α - d -mannopyranosides five methyl l - glycero - α - d - manno -heptopyranosides were synthesized by the one-carbon-atom chain elongation at C-6 and converted to five monophosphates ( 1–5 ) having the PO(OH) 2 group at O-2, -3, -4, -6 and -7. Compounds 1–5 were exposed to acidic and basic hydrolytic conditions used in lipopolysaccharide analysis and the products and their proportion were determined. Under acidic conditions, besides hydrolysis of the glycoside, migrations and hydrolytic cleavage of the phosphate residue were found. Under basic conditions the phosphates were stable.

From suitably protected benzyl α- d -mannopyranosides, five benzyl l -glycero-α- d -manno-heptopyranosides were synthesized by chain-elongation at C-6. By regiospecific protection-deprotection procedures five O-benzylated heptosides having ‘isolated’ free OH groups at C-2, C-3, C-4, C-6, or C-7 were obtained. These substrates were phosphorylated and the products were converted into free monophosphates or monophosphate cyclohexylammonium salts (1–5) which were characterized by 1H, 13C, and 31P NMR spectra and high-performance anion-exchange chromatography.

Syntheses of two derivatives of two 2,4-diamino-2,4,6-trideoxyhexoses having the d -gulo (16) and l -altro (29) configuration have been described. Derivative 16 was obtained by two routes starting from benzyl 2-benzyloxycarbonylamino-2-deoxy-α- d -glucopyranoside. Derivative 29 was obtained from 3,4-di-O-acetyl-l-rhamnal in a 10-step reaction sequence.

Benzyl 2,3- O -isopropylidene-4- O - p -methoxybenzyl-α- d -mannopyranoside was oxidized according to Swern, and the aldehyde obtained was treated with allyloxymethylmagnesium chloride to yield the title heptose derivative ( 7 ) as the main product. This compound had the hydroxyl group at C-6 free. Benzylation yielded the fully protected derivative 9 . O -Deallylation furnished a heptose derivative ( 10 ) having the C-7 hydroxyl group free. Similarly, removal of the p -methoxybenzyl group from 9 led to a derivative ( 11 ) with the C-4 hydroxyl group free. Acid hydrolysis of 9 under controlled conditions led to 2,3-diol ( 12 ). This compound was benzylated under two-phase conditions to yield the 2- O -benzylated product ( 13 ) having a free OH group at C-3. Benzylation of the stannylene derivative obtained from the 2,3-diol and dibutyltin oxide gave the 3- O -benzyl derivative ( 14 ) with HO-2 free. The yields of all steps are good to very good.

Synthesis of the title oligosaccharides was performed with the use of peracetylated l - glycero -β- d - manno -heptosyl trichloroacetimidate as the heptosyl donor and (oligo)glucosyl acceptors bearing acyl and acetal protecting groups.

Methyl 6-deoxy-2,3-O-isopropylidene-α- d -manno-heptofuranoside (9) has been synthesised from the acetyliron complex 2 by a sequence of reactions involving deprotonation of 2, its reaction with aldehyde 5, decomplexation, isolation of 7, and reduction to 9. Compound 9 crystallises in the orthorhombic system, space group P212121, with cell dimensions: a = 6.097(1), b = 7.942(1), c = 26.862(3) A. The intensity data were collected with a Syntex P21 diffractometer. The structure was solved by direct methods and refined by the full-matrix, least-squares procedure, resulting in R = 0.049. The furanoside and 2,3-O-isopropylidene rings are characterised by envelop conformations 5E and E3, respectively. Relatively strong intermolecular hydrogen bonss were observed in the crystal structure.

The title compounds were synthesised, and appropriate derivatives were characterised by GLC, GLC-MS, and NMR spectroscopy. The GLC and GLC-MS data proved 2-O-(6-O-L-glycero-alpha-D-manno-heptopyranosyl-alpha-D-glucopyranosyl)- D- glucopyranose to be a constituent of the outer-core region of the lipopolysaccharide from Escherichia coli K-12, indicating the heptosyl residue to be linked to the terminal glucopyranose residue.

Three approaches to the synthesis of deaminotunicamine and derivatives were developed. Tin tetrachloride condensation of 6-deoxy-1,2:3,4-di-O-isopropylidene-α- d -galacto-heptodialdo-1,5-pyranose with 2-(trimethylsilyloxy)furan gave a mixture of stereoisomeric precursors. Condensation of 1,2:3,4-di-O-isopropylidene-α- d -galacto- hexodialdo-1,5-pyranose with the phosphate carbanion obtained from diethyl (2-furyl)methoxymethyl phosphonate led to 6-deoxy-7-C-(2-furyl)-1,2:3,4-di-O-isopropylidene- l -glycero-α- d -galactoheptopyranose (13). This was converted via the “Δ2”-butenolide route, to a mixture of stereoisomeric 5-C-(6-deoxy-α- d -galactopyranos-6-yl)-pentono-1,4-lactones of the d -allo- and d -talo configuration. In the third approach, 13 was transformed by the “enulose” approach to deamino-tri-(O-isopropylidene)tunicamine.

Methylated or acetylated heptopyranose derivatives were prepared variously from l - glycero - d - manno - and d - glycero - d - manno -heptopyranose, O - l - glycero - a - d - manno -heptopyranosyl-(1 → 3)- l - glycero - d - manno -heptopyranose, O - l - glycero - a - d - manno -heptopyranosyl-(1 → 7)- l - glycero - d - manno -heptopyranose, and O - l - glycero - a - d - manno -heptopyranosyl-(1 → 7)- O - l - glycero - a - d - manno -heptopyranosyl-(1 → 3)- l - glycero - d - manno -heptopyranose, which are structural elements of the heptose region of enterobacterial lipopolysaccharides. Each derivative was investigated by g.l.c. and g.l.c.-m.s., and the retention times and fragmentation patterns were used to identify partial structures of the heptose region of the core oligosaccharide of bacterial LPS.

Vicinal trans-diol groups, present in the pyranose ring, can be converted readily into a double bond by the triphenylphosphine-iodine-imidazole reagent in tolueneacetonitrile solution’*‘. Application of this reaction to benzyl2-benzyloxycarbonylamino-2-deoxy-a-D-glucopyranoside (1) led’ to benzyl2-benzyloxycarbonylamino-2,3,4,6tetradeoxy-6-iodo-a-D-erythro-hex-3-enopyranoside (2) in a high yield and to an unsaturated di-iodo analogue 3 that contained the iodine atoms at C-3 or C-4 and at C-6.

The crystals of the title compound are orthorhombic, space group P212121 (Z = 4) with cell dimensions a = 9.791(1), b = 10.235(1), c = 17.703(2) A. The pyranoid ring has a hybrid twist + screw (0T2+0S5) conformation, and the configuration at C-7 is (R).

Methyl 2-azido-2-deoxy-hexodialdo-1,5-pyranosides of the α-, β- d - gluco and α- d - manno configuration as well as methyl 2-acetamido-2-deoxy-hexodialdo-1,5-pyranosides of the α- and β- d - gluco configuration, protected at positions 3 and 4 with O -benzyl groups were reacted with an excess of allyloxymethylmagnesium or (phenyldimethylsilyl)methylmagnesium chlorides to afford mixtures of C-6 stereoisomeric heptopyranosides. Configuration of the products separated by column chromatography was assigned by 1 H NMR data.

On the basis of 1H and 13C NMR spectroscopy studies, the proportion of pyranose and furanose forms of 6-deoxyheptoses in water solution was determined. Water solution of 6-deoxyheptoses contains all possible furanose and pyranose forms (except 6-deoxy-gluco-heptose for which only pyranose was found), although pyranose is dominant.

The disaccharide L-glycero-D-manno-heptosyl-D-glucose was isolated from the lipopolysaccharide (LPS) of Escherichia coli K-12 strain W3100 after partial hydrolysis with acid, and the structure was determined by methylation analysis, n.m.r. spectroscopy, and comparison with a synthetic standard. In addition, the oligosaccharides L,D-Hep-D-Glc-D-Glc and L,D-Hep-D-Glc-D-Glc-D-Glc were isolated, and their structures were established by g.l.c.-m.s. and methylation analysis. The results indicated that L-glycero-D-manno-heptose, a characteristic constituent of the inner core region, may also occur in the outer core region which, in E. coli, is generally composed of hexoses. A revised structure of the carbohydrate backbone of the hexose/heptose region of the LPS is given.

Condensation of partially protected rhamnobiose derivatives with 1- O -acetyl-2,3,6-trideoxy-α,β- dl - glycero -hex-2-enopyranos-4-ulose afforded pairs of diastereoisomeric α-linked trisaccharide derivatives to which the configuration was assigned on the basis of spectral and chemical data. Reduction of the carbonyl group in these products led to 2″,3″-unsaturated trisaccharide derivatives containing a 2,3-unsaturated α- erythro unit. cis -Hydroxylation of the double bond in five of these unsaturated compounds gave rhamnotriose derivatives, two of which were deprotected to give the trisaccharides α- l -Rha p -(1→2)-α- l -Rha p -(1→3)- l -Rha p and α- d -Rha p -(1→2)-α- l -Rha p -(1→3)- l -Rha p , respectively.

The conformational equilibrium (° H 1 ⇌ 1 H °) has been established for 26 diastereoisomeric methyl 3,4-dideoxy- DL -glyc-3-enopyranosides on the basis of the coupling constant J 1,2 . The position of equilibrium depends on the interplay of steric and polar factors. The concept of the allylic effect is useful in explaining some conformational phenomena.

3,4,6-Tri- O -acetyl- d -galactal, on treatment in 1,2-dichloroethane with alcohols and stannic chloride as catalyst, readily undergoes allylic rearrangement-substitution, forming alkyl 4,6-di- O -acetyl-2,3-dideoxy-α- d - threo -hex-2-enopyranosides in yields of 43-92%. Alkyl 3,4,6-tri- O -acetyl-2-deoxy-αβ- d - lyxo -hexopyranosides are formed as side-products in yields of 2-14 %. Stannic chloride-catalysis is also useful in allylic rearrangement of 3,4,6-tri- O -acetyl-1,5-anhydro-2-deoxy- d - arabino - hex-l-enitol (3,4,6-tri- O -acetyl- d -glucal) which, with methanol or ethanol, affords the corresponding alkyl 4,6-di- O -acetyl-2,3-dideoxy-α- d - erythro -hex-2-enopyranosides in yields of 83 and 94%.

2,6-Diacetamido-2,3,4,6,7-pentadeoxy- dl - ribo -heptopyranose (2,6-di- N -acetyl- dl -purpurosamine B) was synthesized from 6-acetyl-2-methoxy-5,6-dihydro-2 H -pyran in nine steps. The synthesis confirmed the ribo configuration of the natural sugar.

13 C-N.m.r., proton-decoupled spectra of 22 isomeric methyl 3,4-dideoxy- DL - glyc-3-enopyranosides are presented. Comparison of the data for compounds having HO-2 unsubstituted and acetylated enabled assignment of all of the resonances. Specific up- and down-field shifts made possible an unequivocal assignment of structure to 3,4-unsaturated methyl glycenopyranosides. On the basis of the chemical shifts of the signal for C-1, the position of the conformational equilibrium of methyl 3,4-dideoxy- DL -pent-3-enopyranosides could be estimated.

Three methods for the synthesis of the title compounds starting from benzyl 2,3,4-tri-O-benzyl-α- d -manno-hexodialdo-1,5-pyranoside (7 have been elaborated. Conversion of 7 into the cyanohydrin followed by reduction to give the amine and then deamination gave a derivative of l -glycero- d -manno-heptose in low yield. Condensation of 7 with 2-methylfuran gave two stereoisomeric 6-C-(2-methyl-5-furyl) derivatives. The preponderant stereoisomer was ozonised and then reduced to give a derivative of d -glycero- d -manno-heptose. Condensation of 7 with allyloxymethylmagnesium chloride gave derivatives of both heptoses in good yield and with an l -glycero d -glycero ratio of 3.2:1. Deprotection of these derivatives gave the heptoses in high yield.

Benzyl 3-O-benzoyl-4-O-benzyl-2-O-(2,3,6-trideoxy-α- l -glycero-hex-2-enopyranosyl-4-ulose)-α- l -rhamnopyranoside has been investigated by X-ray diffraction methods. The crystals obtained from aqueous ethanol are orthorhombic, space group P212121 with cell constants a = 10.775(2), b = 10.857(2), and c = 25.774(3) A. A four-circle, automatic diffractometer was used for intensity-data collection. Out of 3370 reflection intensities, 2634 were of I > 2σI and these were used for refinement. The structure was solved by direct methods, and the atomic parameters were then refined by the full-matrix, least-squares procedure. The unsaturated dihydropyranone ring adopts a deformed sofa conformation, whereas the rhamnopyranose ring adopts a chair conformation. The glycosidic linkage is characterised by torsion angles Φ33(2)° and Ψ-13(1)°. A new classification for the conformations of glycosidic linkages is suggested.

1,2:3,4-Di- O -isopropylidene-6- O -toluene- p -sulfonyl-α- d -galactopyranose has been investigated by X-ray diffraction methods. The crystals are orthorhombic, space group P 2 1 2 1 2 1 Z = 4) with cell dimensions a = 15.210(2), b = 15.658(2), and c = 8.858(1) A. The structure was solved by direct methods and the atomic parameters were refined anisotropically against 1030 observed reflections by a full-matrix, least-squares procedure giving R 0.039. The pyranoid ring has a twist (° T 2 ) conformation. The 1,2- and 3,4-dioxolane rings were assigned the 3 E and 2 T 1 conformations, respectively. Models of the di- O -isopropylidenegalactopyranose system with minimised strain energy were compared conformationally with several experimental structures containing the above ring systems.

The synthesis of 2-O-α- d -galactopyranosyl- d -galactopyranose was accomplished by condensation of 2,3,4,6-tetra-O-benzyl-α- d -galactopyranosyl chloride with 2,2,2-trichloroethyl 3,4,6-tri-O-benzyl-α- d -galactopyranoside in the presence of mercuric cyanide. The title trisaccharide undeca-acetate was prepared by condensing 1,3,4,6-tetra-O-acetyl-2-O-(3,4,6-tri-O-acetyl-α- d -galactopyranosyl)-α- d -glucopyranose with 2,3,4,6-tetra-O-benzyl-α- d -galactopyranosyl chloride or bromide in the presence of various glycosidation catalysts, followed by debenzylation and acetylation.

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 1 S and 1 R 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 P2 1 ( Z = 2) with cell dimensions a = 14.896(2), b = 8.295(1), c = 20.547(3) A, 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 4 C 1 (tri- O -benzylated moiety) and ° S 5 + ° T 2 (di- O -isopropylidenated moiety). The 1,2- and 3,4- O -isopropylidene rings have 3 T 2 and 2 E conformations, respectively.

6- C -(2-Furyl)-1,2:3,4-di- O -isopropylidene-α- d - glycero - d - galacto -hexopyranose ( 1 ) has been investigated by X-ray diffraction methods. The crystals obtained from ethyl acetate-light petroleum were monoclinic, space group P2 1 ( Z = 2), with cell dimensions a = 13.796(2), b = 7.887(1), c = 8.035(1) A, and β = 106.68(3)°. A four-circle, automatic STOE diffractometer was used for the collection of intensity data. Of 1600 reflection intensities, 1390 were of I > 2σ I and were used for refinement. The structure was solved by direct methods, and the atomic parameters were refined by the full-matrix, least-squares procedure, giving R 0.056. The pyranose ring in 1 adopts a hybrid twist-boat conformation (° T 2 + B 2,5 ).

The repeating units 2-O-beta-D-glucopyranosyl-L-ribitol 4'- and 1-phosphate of Haemophilus influenzae type a capsular antigen have been synthesised by condensation of an alpha-D-glucopyranosyl bromide derivative with 5-O-allyl-1,2,3-tri-O-benzyl-D-ribitol followed by selective deprotection of HO-4' or HO-1, phosphorylation, and removal of the blocking groups.