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Bicyclic amino acids derived from the natural sugars D-arabinofuranose and D-fructofuranose have been synthesised; their ability to induce a turn conformation in peptides has been exploited in the preparation of a cyclic RGD loop mimetic.

We show here that priming and memory generation of antigen-specific CD8+ cytotoxic T lymphocytes (CTL) does not require help if the immunogen binds major histocompatibility complex (MHC) class I molecules with high affinity. This conclusion was based on the study of three chemically distinct optimal length CTL epitopes with high affinity for the restriction element Kb. In contrast, when two subdominant epitopes with intermediate MHC binding affinity were studied, either a class II MHC-restricted T helper cell epitope or administration of antibody to CD40 was required to obtain significant CTL priming. Depending on the epitope, one source of help was much more efficient than the other.

Deprotected C-glycopyranosyl-ketones have been conjugated by a chemoselective approach to a peptide or an amino acid bearing an aminooxy group on the N-terminus or on the side-chain, respectively. The coupling reaction, performed in aqueous media, does not require protecting groups on the peptide or saccharide moieties, nor auxiliary coupling reagents.

The products of a wide variety of organic reactions were rapidly identified by their masses through a combination of thin layer chromatography (TLC) and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS). Crude mixtures of peptides and glycopeptides, complex carbohydrate reactions, and a classical organic reaction were analysed using the following standard protocol. The components of the reaction mixtures were first separated on the TLC plate, scraped off, extracted and analysed by MALDI-TOFMS. The technique used is easy and applicable to most organic reactions, becoming a very powerful technique in reaction optimization once composition and identity of TLC spots have been established by MS. Moreover, the TLC/MALDI-TOFMS method was used to identify low molecular weight compounds with masses within the matrix region (100-500 u), a goal which is normally difficult to achieve. We successfully detected low molecular weight compounds by suppression of the matrix peaks using a relatively low matrix:analyte ratio (15:1 or lower). Doping both matrix and analyte solutions with [Cs]+ ions resulted in suppression of both [Na]+ and [K]+ peaks, thus enhancing the spectral signals and making identification of low molecular weight compounds more facile.

Stable C-glycosidic an analogues of 2-O-(beta-D-glucopyranosyl)-sn-glycerol (In), 2-O-(beta-D-galactopyranosyl)-sn glycerol (Ib), 1-O-(beta-D-glucopyranosyl)-sn-glycerol (7) and their dipalmitoyl ester have been synthesised starting from the corresponding 2,3,4,6-tetra-O-benzyl-glyconolactones 9. The 2-O-derivatives 1 were obtained by methylenation of the lactone 9, reaction of the obtained glycoexoenitol 10 with a malonyl radical, reduction of the malonyl derivative 11 and deprotection. The 1-O-derivative 7 was obtained by reaction of the lactone 9 with butenylmagnesium bromide, reduction of the obtained lactol 14, osmylation and deprotection. (C) 1997 Elsevier Science Ltd.

C-Glycosyl radicals obtained from iodide 1 react with benzo- and naphtho-quinone to afford, after deprotection, C-glycosyl quinones 4 and 6 which inhibit yeast alpha-glucosidase; employing a naphthoquinone linked to the non-reducing end of a sugar 7, a spacer-connected C-disaccharide 8 is obtained.

The synthesis of the disaccharides methyl 4-O-(2'/3'-O-sulfo-beta-D-glucopyranosyluronic acid)-2-amino-2-deoxy-alpha-D-glucopyranoside 3 and 4 as disodium salts is described. Allyl 4,6-O-benzylidene-alpha-D-glucopyranoside 6 was converted to trichloroacetimidate 20. Glycosylation of 20 with 5 promoted by BF3 . OEt(2) gave disaccharide 21. Deacetylation of 21 followed by monoacetylation of the resultant diol 22 afforded the two monoacetylated disaccharides 23 and 24. Sulfation and deprotection of each disaccharide gave the desired sulfated compounds 3 and 4.

C-Glycosyl methylenemalonates 2 and 4, useful precursors for the synthesis of glycopeptides and glycoproteins mimics, are obtained by reaction of a malonyl radical on the glycoexoenitols 1 and 3; reaction of the same radical with 6-deoxy-1,2: 3,4-di-O-isopropylidene-beta-L-arabino- hex-5-enopyranose 5 results in a mixture of the malonylderivatives 6, 7 and 8 and, in diluted THF solutions, also in the tetrahydrofuranyl derivative 9.

The isosteric phosphono analogues of N-acetyl-alpha-D-glucosamine I-phosphate and N-acetyl-alpha-D-mannosamine l-phosphate (1 and 2) are stereoselectively synthesized starting from 2,3,5-tri-O-benzyl-D-arabinose (3b). Reaction of 3b with divinylzinc stereoselectively affords the glucoenitol 4c, the mercuriocyclization and subsequent iododemercuriation of which stereoselectively afford the alpha-C-glucopyranosyl iodide 6b with a free hydroxyl group at C-2. Temporary protection of the hydroxyl group and treatment with triethyl phosphite converts 6b into the corresponding phosphonate 7b. The free hydroxyl group of 7b is then converted into an acetamido group by oximation, acetylation of the oxime, reduction, and subsequent acetylation. The reduction of the oxime with diborane stereoselectively affords the gluco isomer, whereas catalytic hydrogenation gives the manno isomer. Acetylation and deprotection afford the desired products 1 and 2.

Oxidation with pyridinium chlorochromate of the aminoalditols 3 and 5, obtained by reaction of a protected aldose with a primary amine and then with a Grignard reagent, affords alpha-keto-acid derivatives which undergo decarboxylation to lactams 4 and 6. Starting from 2,3,5-tri-O-benzyl-D-arabinose, lactam 4 is the only product, whereas starting from 2,3,4,6-tetra-O-benzyl-D-glucose or -mannose, alpha-keto ester 7 is the main product.

Reaction of 2,3,5-tri-O-benzyl-D-arabinose with divinylzinc, and subsequent mercuriocyclisation and iododemercuriation stereoselectivity affords the alpha-C-glucopyranosyl iodide 3 with a free hydroxy group at C-2; temporary protection of the free hydroxy group, treatment of the iodide with triethylphosphite to afford the corresponding phosphonate, deprotection of the hydroxy group, oxidation, oximation, catalytic hydrogenation and acetylation, afford the phosphono analogue of N-acetyl-alpha-D-mannosamine 1-phosphate.

Pyrrolidines 5a-b, and piperidines 10a,b and 15, were synthesised by Grignard reaction on a glycosylamine, easily obtained from the parent sugar and a primary amine, followed by cyclization with triflic anhydride.

Glycosyl sulfates are easily synthesised from tetrabenzyl pyranoses; their reaction with various accepters promoted by Lewis acids affords glycosides and disaccharides as alpha,beta mixtures.