Phenylpropanoid and iridoid glycosides from Pedicularis lasiophrys.

Two new compounds, pedicularioside E and F, were isolated from whole plants of Pedicularis lasiophrys, along with the four known compounds, verbascoside, cistanoside C, cistanoside D and 8-epiloganin. On the basis of spectral and chemical evidence, pedicularioside E and F were identified to be 1'-O-beta-D-(3-methoxy-4-hydroxy-beta-phenyl)-ethyl-6'-O-feruloyl- alpha-L-(2-acetyl)-rhamnosyl-(1----3')-4'-acetylglucopyranoside and shanzhisin methyl ester cellobioside, respectively.     

Phenylpropanoid and iridoid glycosides from Pedicularis striata.

A new phenylpropanoid glycoside, pedicularioside A, and five known glycosides, acteoside, isoacteoside, decaffeoylacteoside, echinacoside and 8-acetylharpagide, were isolated from whole plants of Pedicularis striata. On the basis of spectral and chemical evidence, pedicularioside A was shown to be 1'-O-beta-D-(3,4-dihydroxy-beta-phenyl)-ethyl-4'-O-caffeoyl-beta-D -apiosyl-(1----3')-alpha-L-rhamnosyl-(1----6')-glucopyranosi de.     

Synthesis of the tetrasaccharide core region of antigenic lipo-oligosaccharides characteristic of Mycobacterium kansasii

The oligosaccharide core region, beta-D-Glcp-(1----3)-beta-D-Glcp-(1----4)-alpha-D-Glcp- 1----1)-alpha-D-Glcp (1), of the lipo-oligosaccharide-type antigens isolated from M. kansasii has been synthesised from 2,3,2',3',4',6'-hexa-O-benzyl-6-O-(1-phenylethyl)-alpha, alpha-trehalose (4). Compound 4 was obtained by LiAlH4-AlCl3-type hydrogenolysis of 2,3,2',3',4',6'-hexa-O-benzyl-4,6-O-(S)-(1-phenylethylidene)-alpha , alpha-trehalose. The beta-laminaribiosyl part of the molecule was built-up by sequential glycosylation steps using 2,4,6-tri-O-acetyl-3-O-allyl-alpha-D-glucopyranosyl bromide in the presence of HgBr2 and methyl 2,3,4,6-tetra-O-acetyl-1-thio-beta-D-glucopyranoside promoted by methyl triflate. The complete a priori 13C-n.m.r. spectrum assignment of 1 was achieved by applying 2D methods.     

Synthesis of a fully protected derivative of O-(N-acetyl-alpha-D-neuraminyl)-(2----3)-O-beta-D-galactopyranosyl-(1- ---3)-O- [(N-acetyl-alpha-D-neuraminyl)-(2----6)]-O-(2-acetamido-2-deoxy-alpha- D-galactopyranosyl)-(1----3)-L-serine

N-(Benzyloxycarbonyl)-O-[methyl (5-acetamido-4,7,8,9-tetra-O-acetyl-3,5-dideoxy-D-glycero-alpha-D-galact o-2- nonulopyranosyl)onate]-(2----3)-O-(2,4,6-tri-O-acetyl-beta-D - galactopyranosyl)-(1----3)-O-[methyl (5-acetamido-4,7,8,9-tetra-O-acetyl-3,5-dideoxy-D-glycero-alpha-D-galact o-2- nonulopyranosyl)onate-(2----6)]-O-(2-acetamido-4-O-acetyl-2- deoxy-alpha-D- galactopyranosyl)-(1----3)-L-serine benzyl ester was synthesized by using O-[methyl (5-acetamido-4,7,8,9-tetra-O-acetyl-3,5- di-deoxy-D-glycero-alpha-D-galacto-2-nonulopyranosyl)onate]- (2----3)-O-(2,4,6- tri-O-acetyl-beta-D-galactopyranosyl)-(1----3)-O-[methyl (5-acetamido-4,7,8,9-tetra-O-acetyl-3,5-dideoxy-D-glycero-alpha-D-galact o-2- nonulopyranosyl)onate-(2----6)]-4-O-acetyl-2-azido-2-deoxy-a lpha- and -beta-D-galactopyranosyl trichloroacetimidate as a key glycotetraosyl donor which, upon reaction with N-(benzyloxycarbonyl)-L-serine benzyl ester, afforded a 44% yield of a mixture of the alpha- and beta-glycosides in the ratio of 2:5.     

Triterpenoid saponins from Sophora subprostrata.

From Sophora subprostrata Radix, the roots of Sophora subprostrata, six triterpenoidal saponins having soyasapogenol A, B, sophoradiol and kuzusapogenol A as aglycones, were isolated as their methyl esters. The structure of a new saponin was established to be 3-O-[alpha-L-rhamnopyranosyl(1----2)-D-galactopyranosyl(1----2)-beta-D- glucuronopyranosyl] kuzusapogenol A methyl ester by means of 1H and 13C NMR spectroscopy and chemical evidence.     

Syntheses of linear tetra-, hexa-, and octa-saccharide fragments of the i-blood group active poly-(N-acetyl-lactosamine) series. Blockwise methods for the synthesis of repetitive oligosaccharide sequences

N-Phthaloylation of lactosamine gave various glycosyl donors (beta-chloride, beta-trichloroacetimidate) and glycosyl acceptors (3',4'-diol). Coupling of the chloride with a methyl beta-D-glycoside led to the tetrasaccharide fragment, beta-D-Galp-(1----4)-beta-D-GlcpNac-(1----3)-beta-D-Galp-(1----4)- beta-D-GlcpNAcOMe. Acetolysis of the protected tetrasaccharide, followed by treatment with hydrogen chloride, gave a tetrasaccharide chloride which was coupled with the methyl beta-glycoside of lactosamine. A hexasaccharide fragment, [beta-D-Galp-(1----4)-beta-D-GlcpNAc-(1----3)]2-beta-D-Galp-(1----4)-bet a- D-GlcpNAcOMe, was thus obtained by this ("n + 1") method. A more efficient ("n + n") method was applied for the synthesis of an octasaccharide fragment, [beta-D-Galp-(1----4)-beta-D-GlcpNAc-(1----3)]3-beta-D-Galp- (1----4)-beta-D-GlcpNAcOMe (38), where di- and tetra-saccharide intermediates having a 3,4-O-isopropylidene-beta-D-galactopyranosyl nonreducing terminal group and a benzyl beta-D-glycoside group were precursors, either as glycosyl donors (beta-trichloroacetimidates) or glycosyl acceptors (3,4-diols as nonreducing terminal groups). Thus, doubling the length of the repetitive oligosaccharide sequence could be efficiently accomplished at each glycosylation step.     

Synthesis of a mucin-type O-glycosylated amino acid, beta-Gal-(1----3)-[alpha-Neu5Ac-(2----6)]-alpha-GalNAc-(1----3)- Ser

Total synthesis of O-beta-D-galactopyranosyl-(1----3)-O-[(5-acetamido-3,5-dideoxy- D-glycero-alpha-D-galacto-2-nonulopyranosylonic acid)-(2----6)]-O-(2-acetamido-2-deoxy-alpha-D-galactopyranosyl)-(1----3 )-L- serine was achieved by use of the key glycosyl donor O-(2,3,4,6-tetra-O-acetyl-beta-D-galactopyranosyl)-(1----3)-O- [methyl (5-acetamido-4,7,8,9-tetra-O-acetyl-3,5-dideoxy-D-glycero-alpha-D-galact o-2- nonulopyranosyl)onate-(2----6)]-4-O-acetyl-2-azido-2-deoxy-a lpha-D- galactopyranosyl trichloroacetimidate and the key glycosyl acceptor N-(benzyloxycarbonyl)-L- serine benzyl ester in a regiocontrolled way.     

Synthesis and structural characterization of the dilactone derivative of GD1a ganglioside

Treatment of GD1a [alpha-Neu5Ac-(2----3)-beta-GalNAc-(1----4)-[alpha- Neu5Ac-(2----3)]-beta-Gal-(1----4)-beta-Glc-(1----1)-Cer] with dicyclohexylcarbodi-imide in anhydrous methyl sulfoxide affords 94-98% of GD1a-dilactone. The involvement of the carboxyl groups of the two sialic acid residues in the lactone rings was proved by ammoniolysis and reduction experiments, which gave ganglioside derivatives containing the amide of sialic acid and N-acetylneuraminulose, respectively. 1H-N.m.r. spectroscopy showed that the lactone rings involved position 2 of each galactose residue in the ester linkages.     

Synthesis, structure, and conformation of the dilactone derivative of GD1b ganglioside

Treatment of DG1b, beta-Gal-(1----3)-beta-GalNAc-(1---- 4)-[alpha-Neu5Ac-(2----8)-alpha-Neu5Ac-(2---- 3)]-beta-Gal-(1----4)-beta-Glc-(1----1)-Cer, with dicyclohexylcarbodi-imide in anhydrous methyl sulfoxide affords 95-98% of GD1b-dilactone. The carboxyl groups of the two sialic acid units are involved in ester linkages, as proved by ammoniolysis and reduction which gave derivatives containing the amide of sialic acid and N-acetylneuraminulose, respectively. 1H-N.m.r. spectroscopy showed that the lactone rings involved position 9 of the inner sialic acid and position 2 of the inner galactose and that the disialosyl chain is extended toward the -beta-Gal-(1 ----4)-beta-Glc- portion of the ganglioside moiety.     

Synthesis of radiolabeled biphenylsulfonamide matrix metalloproteinase inhibitors as new potential PET cancer imaging agents

Novel matrix metalloproteinase (MMP) inhibitor radiotracers, (S)-3-methyl-2-(2',3',4'-methoxybiphenyl-4-sulfonylamino)-butyric acid [(11)C]methyl ester (1a-c), (S)-3-methyl-2-(2',3',4'-fluorobiphenyl-4-sulfonylamino)-butyric acid [(11)C]methyl ester (1d-f), and (S)-3-methyl-2-(4'-nitrobiphenyl-4-sulfonylamino)-butyric acid [(11)C]methyl ester (1g), a series of substituted biphenylsulfonamide derivatives, have been synthesized for evaluation as new potential positron emission tomography (PET) cancer imaging agents.     

Synthesis of methyl glycoside derivatives of tri- and penta-saccharides related to the antithrombin III-binding sequence of heparin, employing cellobiose as a key starting-material

Two key synthons for the title pentasaccharide derivative, methyl O-(methyl 2-O-benzoyl-3-O-benzyl-alpha-L-idopyranosyluronate)-(1----4)-6-O-acetyl- 2-azido - 3-O- benzyl-2-deoxy-beta-D-glucopyranoside and O-(methyl 2,3-di-O-benzyl-4-O- chloroacetyl-beta-D-glucopyranosyluronate)-(1----4)-3,6-di-O-acetyl-2-az ido-2- deoxy-alpha-D- glucopyranosyl bromide, were prepared from a common starting material, cellobiose. They were coupled to give a tetrasaccharide derivative that underwent O-dechloroacetylation to the corresponding glycosyl acceptor. Its condensation with the known 6-O-acetyl-2-azido-3,4-di-O-benzyl-2-deoxy-alpha-D-glucopyranosyl bromide afforded a 77% yield of suitably protected pentasaccharide, methyl O-(6-O- acetyl-2-azido-3,4-di-O-benzyl-2-deoxy-alpha-D-glucopyranosyl)-(1----4)- O- (methyl 2,3- di-O-benzyl-beta-D-glucopyranosyluronate)-(1----4)-O-(3,6-di-O-acetyl-2- azido-2 - deoxy-alpha-D-glucopyranosyl)-(1----4)-O-(methyl 2-O-benzoyl-3-O-benzyl-alpha-L- idopyranosyluronate)- (1----4)-6-O-acetyl-2-azido-3-O-benzyl-2-deoxy-beta-D-glucopyranoside. Sequential deprotection and sulfation gave the decasodium salt of methyl O-(2- deoxy-2-sulfamido-6-O-sulfo-alpha-D-glucopyranosyl)-(1----4)-O-(be ta-D- glucopyranosyl-uronic acid)-(1----4)-O-(2-deoxy-2-sulfamido-3,6-di-O-sulfo-alpha-D-gluco pyranosyl)- (1----4)-O-(2-O-sulfo-alpha-L-idopyranosyluronic acid)-(1----4)-2-deoxy-2- sulfamido-6-O- sulfo-beta-D-glucopyranoside (3). In a similar way, the trisaccharide derivative, the hexasodium salt of methyl O-(2-deoxy-2-sulfamido-6-O-sulfo-alpha-D- glucopyranosyl)- (1----4)-O-(beta-D-glucopyranosyluronic acid)-(1----4)-2-deoxy-2-sulfamido-3,6- di-O- sulfo-alpha-D-glucopyranoside (4) was synthesized from methyl O-(6-O-acetyl-2- azido- 3,4-di-O-benzyl-2-deoxy-alpha-D-glucopyranosyl)-(1----4)-O-(methyl 2,3-di-O- benzyl-beta- D-glucopyranosyluronate)-3,6-di-O-acetyl-2-azido-2-deoxy-alpha-D- glucopyranoside. The pentasaccharide 3 binds strongly to antithrombin III with an association constant almost equivalent to that of high-affinity heparin, but the trisaccharide 4 appears not to bind.     

Synthesis of trisaccharide methyl glycosides related to fragments of the capsular polysaccharide of Streptococcus pneumoniae type 18C.

The synthesis is reported of methyl 3-O-(4-O-beta-D-galactopyranosyl-alpha-D- glucopyranosyl)-alpha-L-rhamnopyranoside (1), methyl 2-O-alpha-D-glucopyranosyl-4-O-beta-D-glucopyranosyl-beta-D- galactopyranoside (3), methyl 3-O-(4-O-beta-D-galactopyranosyl-alpha-D-glucopyranosyl)-alpha-L- rhamnopyranoside 3"-(sn-glycer-3-yl sodium phosphate) (2), and methyl 2-O-alpha-D-glucopyranosyl-4-O-beta-D- glucopyranosyl-beta-D-galactopyranoside 3-(sn-glycer-3-yl sodium phosphate) (4), which are trisaccharide methyl glycosides related to fragments of the capsular polysaccharide of Streptococcus pneumoniae type 18C ([----4)-beta-D- Glcp-(1----4)-[alpha-D-Glcp-(1----2)]-[Glycerol-(1-P----3)]-beta-D-Galp - (1----4)-alpha-D-Glcp-(1----3)-alpha-L-Rhap-(1----]n). Ethyl 4-O-acetyl-2,3,6-tri-O-benzyl-1-thio-beta-D-glucopyranoside (10) was coupled with benzyl 2,4-di-O-benzyl-alpha-L-rhamnopyranoside (6). Deacetylation of the product, followed by condensation with 2,4,6-tri-O-acetyl-3-O-allyl-alpha-D-galactopyranosyl trichloroacetimidate (18), gave benzyl 2,4-di-O-benzyl-3-O-[2,3,6-tri-O- benzyl-4-O-(2,4,6-tri-O-acetyl-3-O-allyl-beta-D-galactopyranosyl)-alpha- D- glucopyranosyl]-alpha-L-rhamnopyranoside (19). Acetolysis of 19, followed by methylation, deallylation (----22), and further deprotection afforded 1. Condensation of methyl 2,4-di-O-benzyl-3-O-[2,3,6-tri-O-benzyl-4-O-(2,4,6-tri- O-acetyl-beta-D-galactopyranosyl)-alpha-D-glucopyranosyl]-alpha-L- rhamnopyranoside (22) with 1,2-di-O-benzyl-sn-glycerol 3-(triethyl-ammonium phosphonate) (24), followed by oxidation and deprotection, yielded 2. Condensation of ethyl 2,3,4,6-tetra-O-benzyl-1-thio-beta-D-glucopyranoside (27) with methyl 3-O-allyl-4,6-O-benzylidene-beta-D-galactopyranoside (28), selective benzylidene ring-opening of the product, coupling with 2,3,4,6-tetra-O-acetyl-alpha-D-glucopyranosyl trichloroacetimidate (31), and deallylation afforded methyl 6-O-benzyl-4-O-(2,3,4,6-tetra-O-acetyl-beta-D-glucopyranosyl)-2-O- (2,3,4,6-tetra-O-benzyl-alpha-D-glucopyranosyl)-beta-D-galactopyranoside (33). Deprotection of 33 gave 3, and condensation of 33 with 24, followed by oxidation and deprotection, gave 4.     

Two synthetic antigens related to Streptococcus pneumoniae type 3 capsular polysaccharide

The synthesis of the allyl beta-glycosides (8 and 20, respectively) of beta-D-GlcpA-(1----4)-D-Glcp and beta-D-Glcp-(1----3)-D-GlcpA (overlapping disaccharide fragments A and B) in the linear chain of the capsular polysaccharide (S3) from Streptococcus pneumoniae type 3 is described. Oxidation of allyl 2,3,6,2',3',4'-hexa-O-acetyl-beta-cellobioside with chromic acid and saponification of the product gave 8. The synthesis of 20 involved glycosylation of methyl 5-O-acetyl-1,2-O-isopropylidene-alpha-D-glucofuranuronate or its 3-O-trityl derivative and subsequent furanose----pyranose transformation. The derivatives 8 and 20 were each copolymerised with acrylamide. In serological tests (enzyme immunoassay and passive hemagglutination), the resulting antigens exhibited the specificity of S3. It was concluded that fragment A was a much stronger immunodeterminant than fragment B.     

Structural characterization of a new anticoagulant fucan sulfate from the brown seaweed Ecklonia kurome.

Methylation analysis of a fucose-containing, sulfated polysaccharide (C-II), which was isolated from the brown seaweed Ecklonia kurome and has a potent anticoagulant activity, showed the presence of 3-O- and 3,4-O-disubstituted fucopyranosyl residues in addition to small proportions of nonreducing, terminal fucofuranosyl and fucopyranosyl groups, and 2,3-di-O- and 2,3,4-tri-O-substituted fucopyranosyl and galactopyranosyl residues with various glycosidic linkages. Methanolysis of C-II gave several neutral oligosaccharide fractions in small proportions and two high-molecular-weight acidic fractions in large proportions. Methylation analysis of the low-sulfated acidic fraction showed that the proportion of 3-O-linked fucosyl residues increases and that of 3,4-O-disubstituted decreased as compared to C-II. Methylation and g.l.c.-m.s. analysis of the neutral oligosaccharide fractions showed the presence of Fuc-(1----3)-Fuc and a fucosyl trisaccharide, in addition to small proportions of Gal-(1----4)-Fuc, Fuc-(1----2)-Fuc, Fuc-(1----4)-Fuc, Fuc-(1----2)-Gal, and Fuc----Gal----Fuc. Methylated C-II was also desulfated by methanolysis, followed by remethylation with (2H3)methyl iodide, and most of (2H3)methyl groups were linked to O-4 of the 3-O-linked fucosyl residues. These results suggested a highly branched, new type of fucan sulfate containing a backbone of (1----3)-linked L-fucosyl residues having sulfate groups mainly attached to C-4.     

Structure of a glycolipid reacting with monoclonal IgM in neuropathy and with HNK-1

An acidic glycolipid antigen that reacts with monoclonal IgM in patients with demyelinating neuropathy and with the mouse monoclonal antibody, HNK-1, was purified from human peripheral nerves. This lipid sharing antigenic determinants with the myelin-associated glycoprotein was shown to be an unusual glucuronic acid-containing sulfated glycosphingolipid with five sugars, but without sialic acid. Mild acid methanolysis converted the GlcUA to its methyl ester, removed the acidic sulfate group and abolished the antigenicity. Results from chemical, enzymatic, infrared, and mass spectral analysis suggested the following structure with a sulfate in a position that remains to be determined: GlcUA beta 1----3Gal beta 1----4GlcNAc beta 1----3Gal beta 1----4Glc beta 1----1 ceramide.     

Synthesis of polydeoxygenated and iodinated disaccharides.]

3-Amino-polydeoxy disaccharides have been prepared by condensation of a glycal with methyl 2,3,6-trideoxy-alpha-L-erythro-(or threo)-hex-2-enopyranoside in the presence of N-iodosuccinimide. After acid hydrolysis of the glycoside, 1,4-addition of hydrazoic acid to the corresponding hex-2-enopyranose led to 3-azido-disaccharides which were acetylated. Reduction of the azido group gave 2,2'-dideoxy- or 2,2'-dideoxy-2'-iodo compounds. Condensation of O-(3,4-di-O-acetyl-2,6-dideoxy-2-iodo-alpha-L-manno-hexopy-rano syl)-(1----4)-1- O-acetyl-2,3,6-trideoxy-3-trifluoroacetamido-alpha-L-arabino-he xopyranose with daunomycinone, followed by 3',4'-O-deacetylation produced the new anthracycline, 7-O-[O-(2,6-dideoxy-2-iodo-alpha-L-manno-hexopyranosyl)-(1----4)-2,3,6- trideoxy-3-trifluoroacetamido-alpha-L-arabino-hexopyranosyl]-da uno-mycinone.     

Structure of novel glyceroglycolipids in Adzuki bean (Vigna angularis) seeds

In addition to monoglycosyl diacylglycerol, three glyceroglycolipids with two to four hexose units were isolated from Adzuki bean seeds. Their structures were determined using enzymatic hydrolysis, permethylation analysis, nuclear magnetic resonance spectroscopy, and reversed-phase high pressure liquid chromatography, as folows: Gal(beta 1----3')- for the monoglycosyl diacyglycerol, Gal(alpha 1----6)-Gal(beta 1----3')- and Gal(beta 1----6)-Gal(beta1----3')- for the diglycosyl diacylglycerol, [Gal(beta 1----6]2-Gal(beta 1----3')- and Gal(beta 1----6)-Gal(alpha 1----6)-Gal(beta 1----3')- for the triglycosyl diacylglycerol, and [Gal(beta 1----6)]3-Gal(beta 1----3')- and [Gal(beta 1----6)]2-Gal(alpha 1----6)-Gal(beta 1----3')- for the tetraglycosyl diacylglycerol. Except for Gal(alpha 1----6)-Gal(beta 1----3')-diacylglycerol, all of the glycolipids with oligosaccharide moieties had novel glycosidic linkage patterns differing from those in the well-known glyceroglycolipids in nature. The predominant diacylglycerol species component was characterized as dilinolenin. However, the molecular species composition of the diacylglycerol moieties of the two diglycosyl isomers with different glycosidic linkage patterns were found to be qualitatively the same but different quantitatively, as follows: in the well-known isomer Gal(alpha 1----6)-Gal(beta 1----3')-, 39% dilinolenin, 15% palmitoyl linolenin, and 14% linoleoyl linolenin; and in the novel isomer Gal(beta 1----6)-Gal(beta 1----3')-, 35% dilinolenin, 24% dilinolein, and 21% linoleoyl linolenin.     

An efficient synthesis of ganglioside GM3: highly stereocontrolled glycosylations by use of auxiliaries

An efficiently stereocontrolled total synthesis of GM3 alpha-D-Neup5Ac-(2----3)-beta-D-Galp-(1----4)-beta-D-Glcp-(1----1) -Cer was achieved by employing both methyl 5-acetamido-4,7,8,9-tetra-O-benzyl-2-bromo-2,3,5-trideoxy-3- phenylthio-D-erythro-beta-L-gluco-2-nonulopyranosonate for the key sialylation step, and O-[methyl(5-acetamido-4,7,8,9-tetra-O-acetyl-3,5-dideoxy-D-glycero-alpha -D-galacto-2-nonulopyranosyl)onate]-(2----3)-O-(2,4,6-tri-O- acetyl-beta-D-galactopyranosyl-(1----4)-3,6-di-O-acetyl-2-O-pivaloyl- alpha-D-glucopyranosyl trichloroacetimidate and fluoride for the key coupling step with a ceramide derivative. These two steps were significantly altered and improved in comparison with our previous synthesis that had been executed without use of stereocontrolling auxiliaries. GM3 was obtained in 4.5% overall yield in 19 steps starting from allyl O-(2,6-di-O-acetyl-3,4-O-isopropylidene-beta-D-galactopyranosyl)-(1----4 )-2,3,6-tri-O-acetyl-beta-D-glucopyranoside.     

Synthesis of the methyl and 1-octyl glycosides of the P-antigen tetrasaccharide (globotetraose)

The methyl and 1-octyl beta-glycosides of the P-antigen tetrasaccharide [globotetraose, beta-D-GalpNAc-(1----3)-alpha-D-Galp-(1----4)-beta-D-Galp-(1----4) -D-Glc] were synthesised from a tetrasaccharide precursor, prepared using methyl disaccharide 1-thioglycosides as intermediates. In the key glycosidation with silver triflate, HO-2 was used as an alpha-directing group in the glycosyl bromide.     

Further definition of the size of the blood group-i antigenic determinant using a chemically synthesised octasaccharide of poly-N-acetyllactosamine type.

In earlier studies, the minimum structure which inhibited the binding of anti-i to an i-active glycoprotein was the linear trisaccharide, beta-D-Galp-(1----4)-beta-D-GlcpNAc-(1----3)-D-Gal. There was an increasing hierarchy of inhibitory activities in the linear tetrasaccharide, beta-D-Galp-(1----4)-beta-D-GlcpNAc-(1----3)-beta-D-Galp-(1----4)-beta-D -GlcNAc , its methyl beta-glycoside, and in the methyl beta-glycoside of the hexasaccharide. The linear octasaccharide methyl beta-glycoside in this series is approximately only half as active as the hexasaccharide methyl beta-glycoside. Analyses by high resolution 1H-n.m.r. of these two oligosaccharides indicated that they have similar conformations in solution, and there is no evidence for the occurrence of inter-molecular interactions which might partially hinder the binding of anti-i to the octasaccharide methyl beta-glycoside. These results are consistent with the size of the i antigen being in the region of a hexasaccharide. It is proposed that the methyl aglycon group of the hexasaccharide methyl beta-glycoside confers an above normal activity by presenting a hydrophobic area for additional contact in the vicinity of the antibody-combining site.