IE48741B1 - Process for the preparation of oside derivatives,the new oside derivatives obtained and their biological applications - Google Patents

Abstract

New process for preparing osides. This process involves the reaction of an ose substituted in position 1 by a-O-imidyl group with an ose containing only a free OH group. Application: preparation of the trisaccharide B.

Description

The invention relates to a new process for the preparation of oside derivatives, the new oside derivatives obtained and their biological applications.

The study of oside derivatives, that is to say of 5 derivatives containing several ose or monosaccharide units, is arousing a considerable interest; in fact, a certain number of them have proved biologically and chemically active or capable of giving rise to such active substances.

It has been shown, inter alia, that some trisacchar10 ides and tetrasaccharides possess a blood group specificity.

Thus, the trisaccharide 2-0-(a-L-fucopyranosyl)3-0-(a-D-galactopyranosyl)-D-galactopyranose of the formula I: constitutes the antigenic determinant B of human blood group.

* Because of this antigenic specificity, this trisaccharide (hereafter referred to as trisaccharide B) finds applications of great importance in various biological areas, in particular in immunohaematology and more especially in the determina5 tion of blood groups.

However, these various applications oan only be carried out on a large scale if trisaccharide B or oside derivatives possessing its structure can be made available easily and with high yields.

Apart from the problem of the synthesis of these products, there is the problem of the form in which they are obtained. In this respect, it will be noticed that, depending on the type of application envisaged, the oside derivative with antigenic specificity can be used as obtained, for example as an antigenic reagent or for preparingatesting serum,or it must contain a substituent chain, more particularly a coupling arm for fixing to a carrier, in order to form, more especially, an artificial antigen or an immunoabsorbent. The problem is therefore to have available an oside derivative with which the various desired applications can easily be carried out. Now, the methods proposed hitherto for the synthesis of oside derivatives constituting antigenic determinants of blood group, and the yields to which they lead, do not prove entirely satisfactory. Fur25 thermore, the products obtained cannot easily be modified for use in a given application.

The study of these problems by the inventors has led them to the development of a new method of steroospecific synthesis which makes it possible to obtain, easily and with an excellent purity and high yields, oside derivatives providing access to numerous biological applications. In a particularly advantageous manner, this method of synthesis makes it possible to obtain branched osides, that is to say osides having oside side-chains, such as trisaccharide B.

This new method of synthesis is all the more valuable because it leads to the production of new oside derivatives, in particular of substitution derivatives of trisaccharide B, some of which can be used, in particular, in the biological applications referred to above.

Advantageously, it is shown that, by virtue of their inherent chemical characteristics, these new derivatives make it easier to carry out these applications, and, in particular, that they can easily be modified in accordance with the des15 ired application or can even be used directly.

The object of the invention is therefore to provide a new process for the synthesis of oside derivatives, which makes it possible easily to make available large amounts of osides and, in particular, branched osides such as tri20 saccharide 3 or substitution derivatives of the latter.

According to another aspect, the object of the invention is to provide new osides, in particular trisaccharide derivatives, and more especially oside derivatives possessing the structure of trisaccharide B.

According to a further aspect, the invention relates to the biological applications of the new oside derivatives.

The process for the synthesis of oside derivatives according to the invention is characterised in that an oside derivative a) which consists of one or more ose units optionally attached, to an organic radical, this ose unit, or at least one of these ose units, being substituted, on the anomeric carbon in the 1-position, by an -O-imidyl group of the formula -O-c(-R2)=N-R-L, in which the substituents R^ and Rg, which are identical or different from one another, represent an alkyl radical and preferably an alkyl radical containing 1 to 4 carbon atoms, and the -OH groups of the oside derivative being protected by suitable groups, is reacted with an oside derivative b) which consists of one or more ose units optionally attached to an organic radical, only one -OH group of this or these ose units being free and occupying any one of the secondary hydroxyl positions 1 to 4, the oside derivatives a) and/or b) comprising one unit having at least two oses.

A process of this type is advantageously employed for the synthesis of derivatives comprising branched osides .

For this purpose, the derivative a), defined above, is reacted with an oside derivative which consists of one or more ose units optionally attached to an organic radical, only one -OH group of this or these units being free and occupying a hydroxyl position 1 to 4 or 6, this permitting the formation of a branched oside chain.

This reaction can advantageously be used for the synthesis of an oside derivative which consists of a branched trisaccharide or comprises such a branched trisaccharide attached, for example,to an organic radical.

According to a preferred method of carrying out the invention, which provides access, in particular, to the production of substances with antigenic properties, an oside ~ 48741 derivative a), which consists of a galactopyranose unit, or a fucopyranose unit, substituted in the 1-position by a group O-imidyl as defined above, is employed in the various embodiments of the above process.

According to a complementary arrangement, the oside derivative b) comprises an ose unit containing, in the 1-position, a substituent -0A consisting of a functional group, which is unreactive under the conditions of the oside synthesis or has been rendered unreactive, or consisting of a group into which functional groups can be introduced, that is to say a group which permits the introduction of functional groups during or at the end of the synthesis.

This essentially implies the availability, in the 1-position, of a group which makes it possible easily to bene15 fit from the properties of the osides obtained, and to do so in the various biological applications referred to below.

Particularly suitable groups A consist of radicals containing one or more unsaturated bonds, such as ethylenically unsaturated radicals. A therefore preferably represents an alkenyl radical containing from 2 to 10 carbon atoms..

A also represents radicals which can be produced, in accordance with the conventional techniques of organic synthesis, by the introduction of functional groups into the unsaturated bond or bonds in question. Radicals of this latter type comprise, for example, alkyl radicals which contain, in particular, 2 to 10 carbon atoms and are substituted by at least one -oh group which, if necessary, is protected by a blocking group or forms part of a functional radical.

A also consists of a functional group containing at least one ether and/or amine radical.

More especially, the process of the invention advantageously employs oside derivatives b) in which the hyd5 roxyl group in the 1-position is substituted by a radical O-allyl, since this group provides access to the introduction of a large number of chemical groups.

Derivatives b) which correspond to the above characteristics and comprise a galactopyranose and/or fucopyranose unit are particularly preferred for the preparation of the products of the invention.

In order to prepare, in accordance with the above preferred procedure, a branched trisaccharide derivative which comprises a galactopyranose-galactopyranose15 fucopyranose linkage and corresponds, more especially, to the structure II: a l-O-imidyl-P-D-galactopyranose of the formula III: (III) is reacted with a disaccharide consisting of a fuco-galactopyranose containing a free -OH group in the 3-position of the galaetopyranose unit, this disaccharide corresponding to the formula IV: In these formulae, the substituents R, which are identical or different from one another, represent groups for protecting hydroxyl radicals, these protective groups incorporating a neighbouring substituent if desired, and are chosen from amongst stable groups which are unreactiveunder the usual conditions of oside synthesis and can readily be removed under mild conditions compatible with the retention of the oside structure, in particular from amongst groups which form, together with the oxygen atom of the hydroxyl, benzyl ethers or benzylidene-acetals, A represents an organic radical as defined above, and R-^ and Rg possess the meanings given above. 487 41 Preferably, the substituent A of the disaccharide of the formula IV consists of an ethylenically unsaturated radical chosen from amongst alkenyl radicals preferably containing from 2 to 10 carbon atoms. A can also consist of an alkyl radical substituted by at least one -OH group which, if necessary, is protected by a blocking group or forms part of a functional radical.

It is particularly preferred to use groups R which represent a benzyl radical and, in the case of the 4- and 6-positions, a benzylidene radical, and to choose an allyl radical as the substituent A.

The choice of these meanings for R and A offers the possibility of removing A independently of R'or of treating it without affecting R, and of converting it to a group which permits the use of the derivative in question in a given biological application. Thus, the allyl group represented by A can be converted, In particular, to a β-hydroxyethyl group, for example under the action of osmium tetroxide and sodium periodate, the value of which group in the biological 2o applications of the products formed will be emphasised below. There is then free scope to remove the groups R when desired. Amongst the wide possibilities for treating the allyl group, its conversion by hydroboration to give a γ-hydroxypropyl group will also be mentioned by way of example. In addi25 tion, such chains can be treated in order to introduce an allyl group which therefore makes It possible to carry out a large number of reactions and to create substitution chains of hydrophilic character, which are particularly valuable for the desired biological applications. It will be > 48741 appreciated that the meaning allyl for A is of great value since this make;, it possible to have available a group which, whilst being unrcactive under the conditions of the oside synthesis, can subsequently be treated easily in accordance with the desired application.

According to one variant, in order to prepare the trisaccharide derivative of the formula II, a digalactopyranose v/hich contains a free -OH group in the 2-position of one of.the galactopyranose units and corresponds to the formula: is employed as the disaccharide, and it is condensed with the group -0-imidyl of a l-O-imidyl-p-L-fucopyranose of the formula VI: . the meanings given above.

The use of this synthesis process leads to the production, with a high yield, of trisaccharide units possessing the desired stereospecificity.

The condensations of the process of the invention 5 are advantageously carried out under anhydrous conditions and at ambient temperature.

The reaction will be carried out in the presence of a strong acid of low nucleophilicity and in a solvent which is weakly nucleophilic and inert with respect to reaction products.

Anhydrous p-toluenesulphonic acid is advantageously used as the acid.

As regards the solvent, it advantageously consists of benzene, ether and, more especially, nitromethane.

The disaccharides employed in the above condensation reactions are new products and constitute synthesis intermediates. These disaccharides are advantageously prepared in accordance with a process which is dependent on the same principle as these condensations.

Thus, in order to obtain the fuco-galactopyranose of the formula (IV), a galactopyranose which contains a free -OH group in the 2-position and corresponds to the formula VII: (VII) is advantageously reacted with a fucopyranose of the formula VI given above, and the group R in the 3-position of the ose unit originating from the galactopyranose VI is then removed in accordance with the conventional techniques for removing the blocking group represented by R.

Similarly, the digalactopyranose of the formula V is advantageously obtained by reacting the galactopyranose of the formula VIII, which contains a free -OH group in the 3-position, with a l-O-imidyl-galaetopyranose of the formula III above.

» The disaccharide thus obtained is then treated, in accordance with the conventional methods, so as to remove the group R in the 2-position of the ose unit originating from the galactopyranose VIII.

According to an aspect of the invention which is of great value, the above process permits a total synthesis of trisaccharide B.

For this purpose, after having carried out the condensations of the disaccharide of the formula IV or V with, respectively, the monosaccharide of the formula III or VI, the substituent A is sequentially removed, under mild conditions in accordance with the conventional techniques, from the resulting product of the structure II, and this leads to a product of the structure IX: ί3 the hydrogenolysis of which makes it possible.to obtain trisaccharide B.

Each of the steps of the synthesis process of the 5 invention is characterised by a high yield. Carrying out these steps thus makes it possible to obtain large amounts of trisaccharide B or of substituted trisaccharides.

According to another aspect of the invention which is of great value, the perfection of the process referred to above leads to the preparation of new oside derivatives.

The study of these new derivatives has shown that, by virtue of their chemical characteristics, they consitute synthesis substances which are analogous to the blood group antigens B; advantageously, these derivatives also provide access to the preparation of antigenic products.

The new osides of the invention contain at least one galactopyranose unit in which the hydrogen atom of the -OH group inthel-position is substituted by a radical A which represents an alkyl group substituted by at least one hydroxyl group which, if necessary, is protected by a blocking group or forms part of a functional radical, or also represents a group containing one or more unsaturated bonds, in particular an ethylenically unsaturated radical chosen from amongst alkenyl radicals, and more especially alkenyl radicals having 2 to 10 carbon atoms, it being possible for A also to contain one or more ether and/or amine groups.

In a preferred group of oside derivatives according to the invention, A represents an alkyl radical which contains 2 to 10 carbon atoms and is substituted by at least- one hydroxyl group, this radical advantageously being chosen from amongst alkylene glycol or hydroxyalkyl radicals.

Products in which A represents an α,β-dihydroxypropyl or β-hydroxyethyl or γ-hydroxypropyl group constitute biological reagents and are also especially valuable in the biological applications which involve fixing these products to a protein or an insoluble carrier, for example for the formation of immunoabsorbent. 2Q In another preferred group of oside derivatives according to the invention, A represents an alkenyl radical containing 2 to 10 carbon atoms and, in particular, an allyl radical. The reactivity of this radical proves very particularly advantageous when carrying out the actual oside synthesis, insofar as A can be treated independently of the blocking groups used for the hydroxyl groups of the ose units. The value of the meaning allyl for A also lies in the range of possibilities offered for the introduction of a given functional group in accordance with the applications envisaged. Ί5 Moreover, it will be noted that the allyl derivative can be used, as obtained, as a biological reagent, for example for neutralising haemolysins. Other preferred products contain a group A comprising at least one ether group and at least one ethylenically unsaturated group which is advantageously an allyl group. In this series of products, A can represent, for example, an alkoxyalkenyl chain and, in particular, an alkoxyallyl chain, the alkoxy group containing a variable number of carbon atoms, which is generally less than 10 and more especially of the order of 3. In a further group of products, A is a radical of the formula -(CH-) -O-(CH„) -Y wherein m and n each represent an integer of from 2 to 10 and y is a group selected from -OH, -OOORj, -COOH, -CONH2, -NH2, wherein R3 is an alkyl radical with 2 to 10 carbon atoms.

The galactopyranose units defined above advantageously form part of a linear or branched trisaccharide chain comprising a fucopyranose unit and another galactopyranose unit.

In these trisaccharide chains, the hydroxyl groups of the various ose units are free or protected by blocking groups chosen from amongst stable groups which are unreactive under the usual conditions of oside synthesis and which can readily be removed under mild conditions compatible with the retention of the oside structure.

The trisaccharides corresponding to the characteristics defined above, and more especially the branched trisaccharides consisting of a galactopyranose unit which contains a substituent A as referred to above and is simultane48741 ously substituted by another galaetopyranose unit and.by a fucopyranose unit, are preferred.

In particular, the invention relates to the branched trisaccharides of the formula II in which the substituents R, which are identical or different from one another, represent groups for protecting hydroxyl radicals, these protective groups incorporating a neighbouring substituent if desired, and are chosen from amongst stable groups which are unreactive under the usual conditions of oside synthesis and can readily be removed under mild conditions compatible with the retention of the'oside structure, and in particular from amongst benzyl or ben2ylidene groups, or represent a hydrogen atom, and A represents an organic radical which contains at least one group into which functional groups can be introduced, and which consists, in particular, of an ethylenically unsaturated radical chosen from amongst alkenyl radicals, preferably having 2 to 10 carbon atoms, and more particularly consists of the allyl radical, or also consists of a hydroxyalkyl radical, and more especially a β-hydroxyalkyl radical in which the group -OH is optionally protected, or represents a substitution chain of the alkoxyalcohol, alkoxy-ester, -amine or -amide, alkoxyalkylamine or amide or alkoxy-carboxylic acid type, it being possible for these various chemical groups to additionally contain an inserted amine group.

As indicated above, these new osides are themselves, or form, intermediates of great value for the preparation of products with blood group properties and, in particular, of trisaccharide B, or of products possessing it’s structure.

The Invention therefore provides the means which make it possible to obtain synthetic homologues of antigen B.

It also provides products which constitute such homologues.

In fact, the trisaccharides of the formula II in which R is a hydrogen atom prove particularly valuable in this respect.

The possibility, afforded by the process of the invention, of having the osides in question available in an extremely pure form imparts even more value to their properties, in particular in their biological applications, especially in immunohaematology and more especially for the determination of blood groups.

The great value of having such synthesis products available, for example for transfusion purposes, will be appreciated by considering the process used hitherto for the determination of blood groups.

According to the most common techniques, these determinations are carried out using testing sera which are of human origin or produced by the immunisation of animals.

Several thousand litres of anti-D antiserum are used each year in France for carrying out the systematic determination of the Rhesus standard group (antigen D). In order for the specificity of this reagent of human origin to be directed solely against antigen D, it is necessary to absorb the natural anti-A and anti-B antibodies, which are initially present in these sera, onto A or B red corpuscles of the Rhesus negative group. Several thousand litres of blood of the Rhesus negative group B are used for this purpose.

This entails not only the handling of very large volumes, but, in particular, involves the use of relatively rare blood.

Thus, in France, only 1.2% of the population belong to the Rhesus negative group B. This has the consequence of causing a shortage, created artificially, of bottles of blood of this group, which are intended for blood transfusion.

The new trisaccharides, of the formula II of the invention, in which R represents a hydrogen atom in fact constitute a solution to this problem of the shortage of bottles of blood belonging to groups which are valuable for blood transfusion.

In fact, by fixing these new trisaccharides to a solid carrier, the invention provides an artificial model, which can be regenerated, of Rhesus negative B corpuscles.

The same type of compound can be used for solving other problems which involve an even rarer occurrence of com25 binations of blood group systems.

For example, some subjects belong to the exceptional group which is negative to Cellano antigen (Kell system) and are capable of developing an anti-Cellano antibody which can be used as a testing serum for Cellano antigen. According to the conventional process for the determination of blood groups, the natural anti-B antibodies of these subjects are absorbed by red corpuscles of a subject of Cellano negative group B. The undeniable value of the use of the compounds of the invention is appreciated by considering that such a combination is only found 1.7 times in 10,000.

It is clear that the use of the immunoahsorbent, defined above, of the invention in place of these red corpuscles, for performing the same function, is of very particular value.

In these applications, carriers which are usually employed in this type of technique, for example active cellulose and the like, can advantageously be used.

The osides of the invention, in particular the osides 20 of the formula II in which A represents an ethylenically unsaturated radical, more especially the allyl radical, or represents a hydroxyalkyl group, can be used as obtained, or optionally modified, as biological reagents.

The study of these derivatives has shown, in particular, 25 that their capacity for neutralising haemolysins is high.

These derivatives can therefore advantageously he used for detecting and neutralising haemolysins, instead of the blood group substances which are isolated, in accordance with the currently used techniques, from stomacin from pig or horse ZO stomach, Other characteristics 'and advantages of the invention will become apparent in the remainder of the description given in the examples.

The melting points given in these examples are measured in a capillary tube by means of a Buchi apparatus and are not corrected. The optical rotations are determined using the model 141 polarimeter marketed by Perkin-Elmer.

The infrared (IR) spectra are recorded using an IRA-1 lo spectrophotometer of Jouan-Jasco and the nuclear magnetic resonance (NMR) spectra are recorded using a Perkin-Elmer R-32 spectrometer (90 MHz). As regards the results relating to NMR, the chemical shifts (δ) are indicated relative to internal tetramethylsilane; the protons of the L-fuco15 pyranose unit bear a single prime and those of the nonreducing D-galactopyranose unit bear a double prime. The column chromatography is carried out using Merck silica gel (particle size 0.063-0.200 mm).

EXAMPLE 1. Preparation of the trisaccharide allyl 2-0-(2,3,420 tri-0-benzyl-a-L-fucopyranosyl)-3-0-(2,3,4,6-tetra-O-benzylα-D-galactopyranosyl)-4,6-Q-benzylidene-p-D-galactopyranoside of the formula X: in which Bz represents the benzyl radical.

In order to prepare the trisaccharide of the formula X, a disaccharide, namely a fucogalactopyranose of the for5 mula XI (allyl 3-0-benzoyl-2-0-(2,3,4-tri-0-benzyl-a-L-fucopyranosyl)-4,6-0-benzylidene-P-D-galactopyranoside): is reacted with the 1-0-imidyl-galactopyranose of the formula XII (l-0-(N-methyl)-acetimidyl-2,3,4,6-tetra-0-benzyl-p-D- 48741 galactopyranose): OBz.

(XII) Prior to this condensation reaction, on the one hand the disaccharide XI, and on the other hand the 1-0-imidyl5 galactopyranose XII, are prepared in accordance with the following procedure. 1. Preparation of the disaccharide XI.

The disaccharide XI is obtained by condensing the fucopyranose of the formula XIII (l-O-(N-methyl)-acetimidyl10 2,3,4-tri-O-benzyl-f3-L-fucopyranose): Cli with the allyl galactopyranose of the formula XIV (allyl. 3-0-benzoyl-4,6-0-henzylidene-p-D-galactopyranoside): a) Preparation of I-0-(N-methyl)-acetimidyl-2,3,4-triO-benzyl-g-L-fucopyranose of the formula XIII. 434 mg of 2,3,4-tri-O-benzyl-cc-L-fucopyranose of the formula XV: obN OBiT-V (XV) OBz are dissolved in 10 ml of methylene chloride, and 2.5 equivalents of dimethylchloroformiminium chloride are then added.

The reaction mixture is stirred in the absence of moisture and is then filtered, after 40 minutes, through a short column of silica gel and evaporated. This yields 2,3,4-tri-O-benzyl-a-L-fucopyranosyl chloride (yield 96%) which is employed directly in the preparation of l-O-(N-methyl)acetimidyl-fucopyranose. 434 mg of this fucopyranosyl chloride and 190 mg of ethyldiisopropylamine are added to 10 ml of an anhydrous benzene solution, which contains 81 mg of N-methylacetamide and is stirred under dry nitrogen and in the absence of light, in the presence of 580 mg of silver oxide and 4 A molecular sieves.

After 20 hours, the reaction medium is filtered on a bed of neutral alumina, which is washed with 250 mg of ether containing 0.1% of triethylamine. The filtrate and the ether phase are evaporated to dryness and the solid residue (462 mg, 94%) is crystallised from hexane, this giving the desired inidate (431 mg, 88%).

Melting point 89~9O°C; [α]ρθ = -67° (c = 1, benzene); NMR (chloroform-d): 61.18 (3H,d,7Hz,Me-C), 1.84 (3H,s,Me-C), 2.97 (3H,s,Me-N), 5-80 (lH,d,Jli28Hz,H-l), 7-30-7.35 (l5H,m,Ph); analysis: calculated for Ο^θΗ^ΝΟ^: C: 73*59; H: 7.20; N: 2.86; 0: 16.34; found: C: 73*72; H: 7*33; N: 2.92; 0: 16.19* b) Preparation of the allyl galactopyranose of the formula XIV.

The preparation is carried out by reacting benzaldehyde, in the presence of zinc chloride, with allyl β-D-galactopyranoside, and this leads to allyl 4,6-0-benzylideneβ-D-galactopyranoside which is subjected to a benzoylation reaction. These steps are carried out as follows: a) allyl β-D-galactopyranoside.

A mixture of 6 g of mercuric oxide, 0.4 g of mercuric bromide and 10 g of drierite is stirred for 30 minutes, at ambient temperature and in the absence of moisture, in the presence of 80 ml of 1,2-dichloroethane and freshly distilled allyl alcohol. 12 g of 1,2,3,4-tetra-0-acetyl-oc-D-galactopyranosyl bromide are then added and stirring is continued for 12 hours. The solids are filtered off and the filtrate is evaporated to dryness .

The residue is dissolved in 200 ml of chloroform and the resulting solution is washed with a 10% strength aqueous solution of potassium iodide and with water, dried (CaClg) and evaporated. The residue is dissolved in 100 ml of methanol, and 3 ml of a molar solution of sodium methoxide in methanol are added.

After one hour, the reaction medium is neutralised (acid resin) and evaporated. The residue is crystallised from ethanol, this giving allyl β-D-galactopyranoside (5.2 g, 81%); melting point 103-104°C; [a]^° = 19° (c = 1, MeOH). β) allyl 4.6-0-benzylidene^-D-galactopyranosi.de. .96 g of allyl β-D-galactopyranoside are then stirred vigorously for 12 hours in the presence of 80 ml of benzaldehyde and 5.5 g of zinc chloride. The reaction medium is then slowly poured, whilst stirring vigorously, into 300 ml of diisopropyl ether. The precipitate formed is filtered off after a few hours and washed with about 100 ml of ether. The resulting solid is crystallised from ethanol, this giving allyl 4,6-0-bengylidene-P-D-galactopyranoside (6.92 g, 82%); melting point 178-179°C, [a]^° = -7° (c = 1, pyridine); analysis; calculated for Cqg^QOgJKLjO: C: 58.88; H: 6.79; 0: 34.31; found: C: 58.94; H: 6.47; 0: 34.09.

This product was characterised by its di-O-acetate: melting point 94-95°C; [α]ρΟ = +56° (c = 1, chloroform); analysis: calculated for C^q^^Oq; C: 61.22; H: 6.16; 0: 32.62; found: C: 61.31; H: 6.12; 0: 32.77.

Y) allyl 3-0-benzoyl-4,6-0-benzylidene-p-D-galactopyranoside A solution of 457 mg of benzoyl chloride in 2 ml of anhydrous chloroform is added, at 5°c, to 5 ml of an anhydrous chloroform solution containing 443 mg of imidazole. After 10 minutes, the imidazole hydrochloride formed is filtered off and washed with 5 ml of chloroform. 20 ml of an anhydrous chloroform solution of allyl 4,6-0-benzylidene5 β-D-galactopyranoside (1 g) are then added to the filtrate and the reaction medium is heated under reflux at 75°C for about 18 hours. After cooling to ambient temperature, the reaction medium is diluted with 50 ml of chloroform, washed with a dilute aqueous solution of bicarbonate and with water, io dried (CaC^) and evaporated. The residue is crystallised from an ethyl acetate/ether mixture, this, giving the compound of the formula XIV (1.14 g, 85%); melting point 172-173°; [a]p° = +83° (c = 1, chloroform)', analysis: calculated for Cg-^i^O?: C: 66.98; H: 5.87; 0: 27.16; found: C: 67.01; H: 5-75; 0: 27.37. c) Condensation of the products obtained under a) and b), A solution of 619 mg of the derivative of the formula XIV in 20 ml of anhydrous nitromethane is stirred for 3 hours, in the absence of moisture and under dry nitrogen, in the pre20 sence of powdered 4 A molecular sieves (1 g). 1.222 g of the acetimidyl fucopyranose XIII and 344 mg of p-toluenesulphonic acid are added to this reaction solution and stirring is continued for 20 hours. The reaction medium is then neutralised with triethylamine and filtered. The filtrate is evaporated and the residue is purified hy chromatography on a column containing I50 g of silica gel, using a hexane/ethyl acetate mixture (5:2, volume/volume). Allyl 3-0-benzoyl2-0-(5,3,4-tri-0-benzyl-a-L-fucopyranosyl)-4,6-0-benzylidene48741 β-D-galactopyranoside is obtained in the pure state (1.131 g, 91%); [a]^° = + 13° (c = 1, chloroform); NMR (chloroform-d.); δ 1.12 (3H,d,7Hz,Me-C), 7.00-7.55 (20H,m,Ph); analysis: calculated for ^θΗ^θΙΐ'* 72.44; Η: 6.32; 0: 21.23; found: C: . 72.66; H: 6.32; 0: 21.27.

This disaccharide is subjected to a selective O-debenzoylation reaction in accordance with the following procedure: 1.03 g of the galactopyranoside derivative in question are dissolved in 20 ml of methanol; and 1 ml of a molar methanolic solution of sodium methoxide Is added. After one hour, the reaction medium is concentrated and poured into ice-cooled water. The phase obtained is extracted with chloroform and the chloroform extracts are then washed with water, dried (CaCl2) and evaporated. The residue is crystallised from an ethyl acetate/ether/hexane mixture, this giving allyl 2-0-(2,3,4-tri-O-benzyl-a-L-fuc opyrano syl)4,6-0-benzylidene^-D-galactopyranoside (847 mg, 94%); melting point 166-167°C; [α]^θ = -58° (c = 1, chloroform)’ NMR spectrum (chloroform-d): δ 1.12 (3H,d,7Hz,Me-C), 5.26 (IH.d.J-L 2,4Hz,H-1'), 7.15-7.65 (20H,m,Ph); analysis: calculated for Ο^Η^θΟ^θ: C: 71-52; H: 6.67; 0: 22.07; found: C: 71.68; H: 6.63; 0: 22.15. 2. Preparation of the 1-0-(N-methyl)-acetimidate of the formula XII.

This imidate is prepared from 2,3,4,6-tetra-0-benzylD-galactopyranose in accordance with the method described under 1-b). The 2,3,4,6-tetra-0-benzyl-a~D-galactopyranosyl chloride formed as an intermediate is obtained with a yield of /8 93%; [“Jj)0 = +151° (c = 2.5, benzene). The imidate is obtained with a yield of 92%; [a]p = +25 (c = 1, chloroform) ; NMR spectrum (chloroform-d): δ 1.84 (3H,s,Me-C), 2.95 (3H,s,Me-N), 5*83 (lH.d,^ 28Hz,H-l), 7.30 (20H,m,Ph); analysis: calculated for C^^H^NOg: C: 74.60; H: 6.94; N: 2.35,· 0: 16.12; found: C: 74.68; H: 6.91; N: 2.10; 0: 16.31. 3. Condensation of the products under 1, and 2.

A solution of the compound allyl 2-0-(2,3,4-tri10 O-benzyl-a-L-fucopyranosyl)-4,6-0-benzylidene-P-D-galactopyranoside (600 mg) and 900 mg of the acetimidate of the formula XII in 15 ml of nitromethane is stirred for 5 hours in the presence of 4 A molecular sieves (1 g) and under a dry nitrogen atmosphere. A solution of anhydrous p-tol15 uenesulphonic acid (150 mg) in 5 ml of nitromethane is then added. The reaction mixture is stirred for 48 hours at ambient temperature. After adding 1 ml of triethylamine, the reaction medium is filtered and the filtrate is evaporated to dryness. The residue is dissolved in 50 ml of chloroform and the solution is washed with a saturated aqueous solution of sodium bicarbonate and with water, dried (CaCl2) and evaporated. The residue is chromatographed on a column containing 80 g of silica gel, using a hexane/ethyl acetate mixture (5:2, volume/volume), this leading to the com25 pound of the formula X (907 mg, 88%) which is crystallised from 95% strength ethanol (865 mg, 84%); melting point 117-118°; [a]20 = +2° (c = 1, chloroform), NMR spectrum (chloroform-d): δ 1.18 (3H,d,THz.CH^-C), 7-05-7.55 (40H,m,Ph); analysis: calculated for ^77^82θΐ5: θ* 74.13; H: 6*62; 0: 19-24; found: C: 74.22; H: 6.64; 0: 19-54.

EXAMPLE 2.

According to a variant, the product of the formula X is prepared by 1. condensing the imidyl galaetopyranose of the formula XII with the allyl galaetopyranose of the formula XVI (allyl 2-0-benzoyl-4,6-0-benzylidene-P-D-galactopyranose): this leading to the disaccharide allyl 2-0-benzoy1-3-0(2,3,4,6-tetra-0-benzyl-oc-D-galactopyranosyl)-4,6-0-benzylidene-p-D-galactopyranoside of the formula: (XVII) and then by 2. condensing the disaccharide of the formula XVII, O-deben15 zoylated beforehand, with the imidyl fucopyranose of the formula XIII. 1. Condensation of the itnidyl galactopyranose of the formula XII with the allyl galactopyranose of the fonnula XVI a) Initially, allyl 2-0-benzoyl-4,6-0-benzylidene-p-D-galactopyranoside is prepared in accordance with the following procedure: ml of an ice-cooled solution of sodium hydroxide are added to 15 ml of an acetone solution containing 1.5 g of the compound of the formula XIV. After two minutes, the reaction medium is extracted with 80 ml of chloroform and the organic extracts are washed with water, dried with CaCl2 and evaporated. The residue is chromatographed on a column containing 80 g of silica gel, using an ethyl acetate/hexane mixture (1:1, volume/volume). This, yields the starting material (782 mg, 52%) and the desired derivative (661 mg, 44%); melting point 144-145°C; = +10.2° (c = 1, chloroform); analysis: calculated for θ23^24θ7': 66.98; Η: 5·θ7; 0: 27.16; found: C: 67.04; Η: 6.03; N: 27.12. b) The galactopyranoside thus formed is converted to the galactosyl derivative using the compound of the formula XII.

The reaction is carried out in accordance with the technique described above, 285 mS of tbe galactopyranoside and 596 mg of the imidate being employed.

After purification on a column containing silica gel (carried out with 40 g of silica and a 2:1 volume/volume ethyl acetate/hexane mixture), 594 mg of the desired disaccharide are obtained, this corresponding to a yield of 95%; [a]p° = +80.5° (c = 1, chloroform); NMR spectrum (chloroform-d): 6 4.63 (lH.d.J^ 29Hz,h-1), 5.13 (lH,d,Jlt 2,4Hz,H-1’); analysis: calculated for Ο^γΗ^θΟ^: θ: 73.21; Η: 6.25; 0: 20.53; found: C: 73.06; H: 6.02; 0: 20.71. c) The resulting disaccharide is subjected to a selective O-debenzoylation. 580 mg of the disaccharide are dissolved in 20 ml of methanol and the solution is then treated with 1 ml of a 1M methanolic solution of sodium methoxide. After 12 hours, the reaction medium is concentrated, diluted with 50 ml of chloroform and then washed with water, dried with CaClg and evaporated. The residue is crystallised from 95° strength methanol. This yields 479 mg, which is a yield of 93% of the O-debenzoylated disaccharide; melting point 150-151°C; [cc]^° = +44° (c = 1, chloroform); NMR spectrum (chloroform-d): δ 2.86 (lH,d,J3Hz,0H), 5.21 (lH.d.Jp 2,4Hz,H-l'), 7.10-7.60 (25H,m,Ph); analysis: calculated for C: 72.27; H: 6.55; 0: 21.18; found: C: 72.46; H: 6.52; 0: 21.29. d) In accordance with the technique described above, the trisaccharide of the formula X is prepared by condensing the disaccharide of the formula XVII with the crystalline iraidate of the formula XIII, these compounds being employed in respective amounts of 275 and 325 mg. This yields 370 mg of trisaccharide, which corresponds to a yield of 79%; melting point 115-116°C; [a]§° = +2° (c = 1, chloroform). « 48741 EXAMPLE 3· Preparation of 2-0-(2,3,4-tri-O-benzyl-2-L-fucopyranosyl)-3-0-(2,3,4,6-tetra-O-benzyl-oc-D-galactopyranosyl)4,6-0-benzylidene-D-galactopyranose of the formula; 624 mg of the trisaccharide of the formula X are dissolved in 10 ml of dimethylsulphoxide. The reaction mixture thus formed is stirred for about 4 hours at 100°C in the presence of 294 mg of potassium tert.-butoxide.

After cooling to ambient temperature, the reaction medium is poured into a 10% strength ice-cooled aqueous solution of ammonium chloride; the resulting solution is extracted with 60 ml of chloroform and the chloroform extracts are washed with water, dried with CaClg and evaporated. The residue is dissolved in 20 ml of an acetone/water mixture (9:1, volume/volume) and the solution is then stirred for 30 minutes in the presence of 428 mg of yellow mercuric oxide and 271 mg of mercuric chloride. After filtration, the reaction 8 7 41 medium is washed with a 10% strength aqueous solution oi potassium iodide and with water, dried with CaCl2 and then evaporated. The residue is chromatographed on a column containing silica gel (50 g), using a hexane/ethyl acetate mixture(3:2, volume/volume). 495 mg of the desired trisaccharide (yield 82%) are thus obtained in the form of a colourless foam; [α]^θ = +50° (c = 1, methanol); NMR spectrum (chloroform-d): δ 2.99 (3H.d.7Hz.CH^-C). 5.56 (1H,s,CH-Ph), 7.05-7.65 (40H,m,Ph); analysis: calculated for Ογ/,ΗγθΟ·^: C: 73-61; H: 6.51; 0: 19.87; found: C: 73.80; H: 6.58; 0: 20.06.

EXAMPLE 4. Preparation of trisaccharide B or 2-0-(a-L-fucopyranosyl)-3-0-(g-D-galactopyranosyl)-D-galactopyranose of the formula: 480 mg of the trisaccharide of the formula XIX are subjected to hydrogenolysis for about 20 hours, at ambient temperature and at atmospheric pressure, in 20 ml of acetic acid, in the presence of 500 mg of palladium-on-charcoal. After filtering off the catalyst, the filtrate is evaporated to dryness at a temperature below 35°C, this giving the des5 ired trisaccharide (186 mg, 96?$) in the form of a white powder; melting point 135~138°C (decomposition); [α]ρθ = +35° (c = 1, water:methanol, 19:1, volume/volume); NMR spectrum (DgO): δ 1.70 (3H,d,7Hz,CHj-C).

This compound is characterised by its crystalline per acetate; melting point 215-216°C; [a]p° = +51° (c = 1, chloroform); NMR spectrum (chloroform-d): δ 1.17 (3H,d,6.5Hz,Me-C), 1.90-2.20 (30H,m,Ac), 6.40 (lHjd.J^ 23·5Ηζ.Η-1, a anomer).

EXAMPLE 5. Preparation of β-hydroxyethyl 2-0-(2,3,4-tri15 0-benzyl-a-L-fucopyranosyl)-3-0-(2,3,4,6-tetra-O-benzylα-D-galactopyranosyl)-4,6-0-benzylidene-p~D-galactopyranosi de of the formula XX: 312 mg (0.22 mol) of trisaccharide X are stirred, at ambient temperature, in 16 ml of a dioxane/water mixture (3:1, volume/volume) to which 1.25 mg of osmium tetroxide (OsO^) are added. After one hour, 112 mg, 2.1 equivalents, of sodium periodate (NalO^) are added and the mixture is then stirred for about 4 hours. mg of sodium borohydride (NaBH^) are added and then, after 10 minutes, the mixture is evaporated to dryness and the residue is taken up in about 100 ml of chloroform.

This chloroform solution is washed with a 10% strength aqueous solution of sodium sulphite (NagSOj) and then with water. It is subsequently dried over calcium chloride (CaClg) and then filtered, and the filtrate is evaporated. This yields a syrup which is treated with 16 ml of a dioxane/water mix15 ture (3:1, volume/volume) and stirred with 52 mg (1 equivalent) ofNalO^ After 3 hours, 50 mg of NaBH^ are added and then, after 10 minutes, the mixture is evaporated to dryness and the residue is taken up in 100 ml of chloroform. The chloroform solution is washed as indicated above.

The resulting syrup is chromatographed on 20 g of silica (SiOg). A mixture of ethyl acetate and hexane (3:1, volume/volume) is used as the eluent.

The product collected after evaporating off the elu25 ent is recrystallised from an ether/hexane mixture. This yields 247 mg of the desired trisaccharide; melting point 83-84°C; yield 79%.

EXAMPLE 6. Preparation of T-hydroxypropyl 2-0-(2,3,4-triO-benzyl-a-L-fucopyranosyl)-3-0-(2,3,4,6-tetra-O-benzylα-D-galactopyranosyl)-4,6-0-benzylidene-p-D_galactopyranoside of the formula XXI: 312 mg (0.25 mmol) of the trisaccharide XX are stirred, at ambient temperature, in anhydrous tetrahydrofuran (3 ml), and 0.8 ml of a 0.5M solution of 9-borabicyclo[3.3.ljnonane, or 9-BBN, in tetrahydrofuran is added. After heating under reflux for 4 hours and cooling to ambient temperature, the excess 9-BBN is destroyed by adding ethanol (0.3 ml).

A 3M aqueous solution of sodium hydroxide (0.2 ml) is subsequently added and 0.2 ml of a 10M solution of hydrogen peroxide is then added dropwise, the temperature being kept at between 40 and 50°C . The reaction mixture is then heated at 50° for 1 hour, whilst stirring. After cooling, solid potassium carbonate (1 g) and methylene chloride (20 ml) are added. The solids are filtered off and the filtrate is evaporated . The residue is purified by passing it through a column containing silica gel (15 g) and eluting it using an ethyl acetate/hexane mixture (2:1, volume/volume). The compound XXI is thus obtained in the pure state (292 mg, 92%); [a]^° = +2° (c = 1, chloroform).

This compound is characterised by its crystalline acetate; melting point 112-113°; [α]^θ = +1.5° (c = 1, chloroform); NMR spectrum (chloroform-d): δ 1.20 (3H,d,6.5Hz,Me-C), 2.00 (s,3H,AC), 7.10-7.60 (40H,m,Ph). EXAMPLE 7. Preparation of T-allyloxypropyl 2-0-(2,5.4-tri10 O-benzyl-a-L-fucopyranosyl)-3-0-(2,3,4,6-tetra-0-benzyla-D-galactopyranosyl)-4,6-0-benzylidene-P-D-galactopyranoside of the formula XXII: 633 mg of the compound XXI are stirred, at ambient 15 temperature, in N,N-dimethylformamide (10 ml), in the presence of sodium hydride (96 mg of a 50% strength dispersion in oil). After one hour, allyl bromide (0.I5 ml) is added. The reaction is complete in 1 hour 30 minutes. After adding methanol (2 ml), the reaction medium is evaporated and the residue is taken up in chloroform (50 ml). The organic phase is washed with a saturated aqueous solution of sodium chloride and with water, dried over sodium sulphate and filtered, and the filtrate is evaporated. The oil present in the residue is extracted with boiling hexane (20 ml) and the desired compound is crystallised from an ethyl acetate/ hexane mixture (588 mg, 9C%); melting point 103-104°; = +3° (c = 1, chloroform); NMR spectrum (chloroform-d) δ 1.21 (3H,d,J7Hz,Me-C), 7.10-7.55 (40H,m,Ph).

EXAMPLE 8. Preparation of T-f(Y-hydroxy)-propoxy1-propyl 2-0-(2,3,4-tri-O-benzyl-α-L-fucopyranosyl)-3-0-(2,3,4,6-tetra- 490 mg of the derivative XXII are stirred, at ambient 15 temperature, in anhydrous tetrahydrofuran (4 ml), and 1 ml of a 0.5M solution of 9-BBN in tetrahydrofuran is added. After heating under reflux for 2 hours 30 minutes and cooling to ambient temperature, the excess 9-BBN is destroyed by adding ethanol (1 ml). A 3M aqueous solution of sodium hydroxide (0.25 ml) is subsequently added and 0.30 ml of a 10M solution of hydrogen peroxide is then added dropwise, the temperature being kept at between AO and 50°C. The reaction mixture is then heated at 50° for 1 hour. After cooling, the aqueous phase is saturated with potassium carbonate (1 g) and filtered, and the filtrate is evaporated.

The residue is purified bypassing it through a column containing silica gel (30 mg) and eluting it using an ethyl acetate/ hexane mixture (2:1, volume/volume). The compound XXIII is thus obtained in the pure state (442 mg, 89%); = +1.5° (c = 1, chloroform); NMR spectrum (chloroform-d): δ 1.20 (3H,d,6.5Hz,Me-C), 7.60-7.70 (40H,m,Ph).

EXAMPLE 9« Preparation of the compound of the formula XXIV: (XXIV) XXIV Dry chromium trioxide (400 mg) is added, whilst stirring and in the absence of moisture, to a mixture of methylene 4.j chloride (15 ml) and pyridine (0.644 ml). After stirring for 20 minutes, a solution of the trisaccharide XXI (633 mg) in methylene chloride (5 ml) is added. After 20 minutes, the reaction medium is decanted and the residue is extracted with chloroform. The chloroform phase is washed with a saturated solution of sodium bicarbonate and with water, dried over sodium sulphate and filtered)and the filtrate is evaporated. The residue is purified by chromatography on silica gel (10 g) using an ethyl acetate/hexane mixture (3:1, volume/volume). The resulting aldehyde (575 mg, 91%) is converted into the derivative XXIV by means of a conventional Wittig reaction in benzene (15 ml). This derivative is crystallised from ether/hexane (524 mg, 88%); melting point 152-153°; [a]20 = -3° (c = Ϊ, chloroform); NMR spec15 trum (chloroform-d): δ 1.23 (3H,d,6.5Hz,Me-C), 3-69 (3H,s,C00Me), 7.10-7.55 (40H,m,Ph).

EXAMPLE 10.

Application of the products of the invention as immunoabsorbents. 2o 1· Activated agarose covered with human serum albumin (HSA) is used. The agarose is activated with CNBr in accordance with Axen et al., Nature 214, 1,302, 1967, and March et al., Annal. Bio., 60, 149 (1974). The agarose is covered with HSA in accordance with the method of Parikh et al., Methods in Enzymology, 35, 77 (1974). The derivative XXIV is coupled with the matrix using a carbodiimide derivative, the reaction being carried out in accordance with the above method of Parikh. 10 to 20 molecules of the product XXIV are thus introduced per molecule of albumin. 2. Activated agarose, which has been converter to an aminoalkyl derivative using ethylenediamine, the reaction being carried out in accordance with Cohen in Methods in Enzymology, 35, 102 (1974), is used as the carrier, the pro5 duct XXIV is coupled as indicated above and the product is then acetylated in order to remove the excess amino group. 3. A derivative of the formula II in which R is a hydrogen and A is a group -(CHg^-O-iCHg^-NHg is fixed to carboxymethylcellulose and the product is then coupled with the carbodiimide as described above.

EXAMPLE 11.

Use of the product XXIV for neutralising anti-B haemolysins.

A solution containing 10 mg/ml of the product XXIV 15 is used. By carrying out the reaction in accordance with the techniques of the European Pharmacopoeia, a total inhibition of an agglutinant dose of an anti-B testing serum is observed with a 1/5 dilution of the product of the invention.

Claims (25)

1. Process for the preparation of oside derivatives, characterised ir. That an oside derivative a) which consists of one or more ose units optionally attached to an organic 5 radical, this ose unit, or at least one of these ose units, being substituted, on the anomeric carbon in the 1-position, by an -O-imidyl group of the formula -O-C(-Rg) = N-R^, in which the substituents R-^ and Rg, which are identical or different from one another, represent an 10 alkyl radical preferably containing 1 to 4 carbon atoms, and the groups -OH of the oside derivative being protected by suitable groups, is reacted with an oside derivative b) which consists of one or more ose units optionally attached to an organic radical, only one -OH group of this or these ose 15 units being free and occupying any one of the secondary hydroxyl positions 1 to 4, the oside derivatives a) and/ or b) comprising one unit having at least two OSes.

2. Process for the preparation of oside derivatives, characterised in that, in order to obtain branched osides, 20 the oside derivative a) 5 according to Claim l,is reacted with an oside derivative which consists of one or more ose units optionally attached to an organic radical, only one -OH group of this or these units being free and - occupying a hydroxyl position 1 to 4 or 6, this permitting the formation 25 of a branched oside chain.

3. Process according to Claim 1 or 2, characterised in that the oside derivative a) employed consists of a galactopyranose unit.

4. Process according to Claim 1 or 2, characterised i- that the oside derivative a) consists of a fucopyranose ori

5. Process according to any one of Claims 1 to 4, characterised in that the oside derivative b) comprises ar ose unit containing, in the 1-position, a substituent -0A consisting of a functional group which is unreactive under the conditions of the oside synthesis or has been rendered unreactive, or consisting of a group into which functional groups can be introduced, that is to say a group which permits the introduction of functional groups during or at the end of the synthesis.

6. Process according to Claim 5, characterised in that, in the substituent -0A, A represents a radical containing one or more unsaturated bonds, such as an ethylenically unsaturated radical, preferably an alkenyl radical containing from 2 to 10 carbon atoms, and also represents any radical which can be produced, in accordance with the conventional techniques of organic synthesis, by the introduction of functional groups into the unsaturated bond or bonds in question.

7. Process according to Claim 5, characterised in that, A represents an alkyl radical which contains, 2 to 10 carbon atoms and is substituted by at least one -OH group which, if necessary, is protected by a blocking group or forms part of a functional radical.

8. Process according to Claim 5, characterised in that A represents the allyl radical.

9. Process according to Claim 5, in which A is a functional group containing at least one ether and/or amine radical.

10. Process for the preparation of a branched trisaccharide derivative which comprises a galactopyranosegalactopyranose-fucopyranose linkage and corresponds to the characterised in that a l-O-imidyl-p-D-galactopyranose of the formula III: = Ν' (III) is reacted with a disaccharide consisting of a fuco-galacto10 pyranose containing a free -oh group in -the 3-position of the galactopyranose unit, this disaccharide corresponding to the formula IV: 4-5 in which formulae: the substituents R, which are identical or different from one another, represent groups for protecting hydroxyl radicals, these protective groups optionally 5 incorporating a neighbouring substituent, and are chosen from amongst stable groups which are unreactive under the usual conditions of oside synthesis and can readily be removed under mild conditions compatible with the retention of the oside structure, in particular from amongst groups 10 which form, together with the oxygen atom of the hydroxyl, benzyl ethers or benzylidene-acetals, A represents an organic radical as defined in any one of Claims 6 to 8, and R-^ and R^ possess the meanings given in Claim 3. * 48741

11. Process for the preparation of the trisaccharide derivative of the formula II, according to Claim 10,character ised in that a digalactopyranose which contains a free -OH groip in the 2-position of one of the galaetopyranose units and 5 corresponds to the formula V: is employed, and in that it is condensed with the group -O-imidyl of a l-O-irr.idyl-p-L-fucopyranose of the formula VI: 10 5χ» Sp’ — Δ possessing, in these formulae, the meanings given in Claim 1Ό.

12. Process according to Claim 10 or 11, characterised in that the substituent A of the disaccharide of the formula IV consists of the allyl radical, 15

13. Process according to any one of the preceding claims, characterised in that the reaction is carried out in the 48742 presence of anhydrous p-toluenesulfonic acid and nitromethane .

14. Application of the process according to any one of Claims 10to 13 to the synthesis of trisaccharide B, character5 ised in that the substituent A is sequentially removed, under mild conditions in accordance with the conventional techniques, from the resulting product of the structure II, which leads to a product of the structure IX: 10 quid this is followed by hydrogenolysis.

15. osides as obtained by reacting an oside derivative a) which consists of one or more ose units optionally attached to an organic radical, this ose unit, or at least one of these ose units, being substituted, on the anomeric carbon in the 1-position, by an -O-imidyl group of the forrnula-O-C (-R 2 ) =N-R 3 , in which the substituents R^ and Rg, which are identical or different from one another, represent an alkyl radical preferably contain5 ing 1 to 4 carbon atoms, and the -OH groups of the oside derivative being protected by suitable groups, with an oside derivative b) which consists of one or more ose units optionally attached to an organic radical, only one -OH group of this or these ose units being free and occupying any one of the secondary hydroxyl positions 1 to 4, the oside derivatives a) and/or b) comprising one unit having at least two oses, said oses being characterized by the fact that they contain at least one galactopyranose unit in which the hydrogen atom of the -OH group in the 1-position is substituted by a radical A which represents an alkyl group substituted by at least one hydroxyl group which, if necessary, is protected by a blocking group or forms part of a functional radical, or represents a group containing one or more unsaturated bonds, in particular an ethylenically unsaturated 2q radical chosen from amongst alkenyl radicals, and more especially alkenyl radicals having 2 to 10 carbon atoms or A is a radical of the formula -(CH O ) -O-(CH_) -Y wherein m z m i n and n each represent an integer of from 2 to 10 and Y is a group selected from -OH, -COOR^, -COOH, -CONHg, -NHg, wherein R 3 is an alkyl radical with 2 to 10 carbon atoms.

16. Osides according to Claim 15, characterised in that the radical A is as defined in one of Claims 7 to 9.

17. Osides according to Claim 16, characterised in that the said galactopyranose unit forms part of a linear or branched trisaccharide chain comprising a fucopyranose unit and another galactopyranose unit.

18. Osides according to Claim 17, characterised in 5 that they are branched trisaccharides of the formula II: 1 in which: the substituents R, which are identical or different from one another, represent groups for protecting hydroxyl radicals, these protective groups incorporating a neighbour10 ing substituent if desired, and are chosen from amongst stable groups which are unreactive under the usual conditions of oside synthesis and can readily be removed under mild conditions compatible with the retention of the oside structure, and in particular from amongst benzyl or benzylidene groups, 15 or represent a hydrogen atom, and A represents an organic radical which contains at least one group into which functional groups can be introduced, and which consists, in particular, of an ethylenically unsaturated radical chosen from amongst alkenyl radicals, preferably having 2 to 10 carbon atoms, and more particularly consists of the allyl radical, or also consists of a hydroxyalkyl radical, and more especially a β-hydroxyalkyl radical, γ-hydroxypropyl, γ-allyloxypropyl, 5 Y/*(7-hydroxy) propyloxy/ propyl , a —CH2—CH^CH=CH—COOCH^ or —( CH 2^3— 0 —(CH2)yNH 2 group, the —OH group (s) being optionally protected or blocked.

19. The trisaccharides according to Claim 18, in which the various substituents R represent hydrogen atoms. 10

20. The trisaccharides of the formula II according to Claim 18, in which A is an allyl group.

21. Application of the trisaccharides according to Claim 2o to the synthesis of trisaccharide B in accordance with the process of Claim 14. 15

22. Osides according to any one of Claims 14 to 18, for use as immuno-absorbents or for the formation of an artificial antigen.

23. Osides according to any one of Claims 15 to 20, in the free form or immobilised on a carrier 20 for use in the formation of biological reagents, in particular for the detection and the neutralisation of haemolysins and the preparation of testing sera possessing a given specificity.

24. Process as claimed in Claim 1 or 2, for the pre25 paration of oside derivatives, substantially as herein described.

25. Oside derivatives, whenever prepared by a process claimed in a preceding claim.