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202 results on '"GAREGG, P. J."'

7. A facile approach to diosgenin and furostan type saponins bearing a 3 beta-chacotriose moiety

Author

Lahmann, Martina, Gyback, H, Garegg, P J, Oscarson, S, Suhr, R, Thiem, J, Lahmann, Martina, Gyback, H, Garegg, P J, Oscarson, S, Suhr, R, and Thiem, J

Abstract

Combination of a one-pot coupling technique and the use of benzyl ethers as permanent protecting groups offered a short and simple route to dioscin-type saponins. This strategy in combination with a mild reductive opening procedure of the spiroketal function in diosgenin also offered a convenient approach to bidesmosidic furostan type saponins. (Me3NBH3)-B-./AlCl3 promoted acetal opening of 3-O-TBDMS-protected diosgenin gave the 26-OH acceptor 9 into which a benzylated beta-glucose moiety was introduced by a S(N)2-type imidate coupling. After cleavage of the silyl ether, the 3beta-O-glucose and the 4-O-linked rhamnose of the chacotriose unit were introduced by a NIS/AgOTf-promoted one-pot coupling sequence utilising thioglycoside donors and their different reactivity in different solvents. After removal of a benzoyl group, the same coupling conditions were also used for the coupling of the second 2-O-linked rhamnose unit. The target substance was obtained after cleavage of the protecting benzyl ethers under Birch-type conditions, which did not affect the double bond in the steroid skeleton., QC 20230602

Published
2002
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8. Synthesis of a polyphosphorylated GPI-anchor core structure

Author

Lahmann, Martina, Garegg, P J, Konradsson, P, Oscarson, S, Lahmann, Martina, Garegg, P J, Konradsson, P, and Oscarson, S

Abstract

Using a linear assembly approach a highly differentially protected derivative of the common GPI-anchor core structure (alpha-D-Man-(1-->6)-alpha-D-Man-(1-->2)-alpha-D-Man-(1-->4)-alpha-D-GlcNH(2)-(1-->6)-D-myo-inositol) has been synthesized. All mannose donors were prepared from a common thioglycoside precursor (1), and coupled to GlcN(3)-myo-inositol acceptor 5 in a linear five-step glycosylation-deprotection sequence in 49% overall yield, to give the key intermediate 10, with orthogonal temporary protecting groups at the 6", 2", 6', and 2 positions of the trimannoside motif and at the 1 and 2 positions of the inositol part. Consecutive removal of the temporary protecting groups in the trimannoside moiety followed by phosphorylation, gave a tetraphosphosphate derivative in 60% overall yield. Removal of a camphor acetal afforded a 1,2-inositol diol, which was converted to a 1,2-cyclic phosphate using commercial methyl dichlorophosphate (-->17, 95%). One-step deprotection using sodium in liquid ammonia afforded the target polyphosphorylated core structure 18 (60%), which will be tested for metabolic insulin action., QC 20230602

Published
2002
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29. Synthesis of an artificial antigen that corresponds to a disaccharide repeating unit of the capsular polysaccharide of Haemophilus influenzaetype d. A facile synthesis of methyl 2-acetamido-2-deoxy-β-d-mannopyranoside

Author

Classon, Björn, Garegg, Per J., Oscarson, Stefan, and Tidén, Anna-Karin

Abstract

The synthesis is described of p-nitrophenyl 2-acetamido-3-O-(2-acetamido-2-deoxy-β-d-glucopyranosyl)-2-deoxy-β-d- mannopyranosiduronic acid, corresponding to the disaccharide repeating unit of the capsular polysaccharide of Haemophilus influenzaetype d, which, after conversion of the p-nitro- into a p-amino-phenyl residue, may be attached to a protein to make an artificial antigen for immunological studies. The synthesis incorporates a facile route to the 2-acetamido-2-deoxy-β-d-mannopyranosyl unit.

Published
1992
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31. An Unusual Cyclic System: Derivatives of N-Acetyl [2-Deoxy-β-D-Mannopyranosid]Urono-6,2-Lactam

Author

Garegg, Per J.

Abstract

ABSTRACTSyntheses are described of a new ring system, namely derivatives of N-acetyl [2-deoxy-β-D-mannopyranosid]urono-6,2-lactam. These were formed by participation of a 2-acetamido-2-deoxy group in the oxidation using pyridinium dichromate of a 6-hydroxyl group in a mannopyranosidic system The structures of the new compounds were determined mainly by NMR experiments inter aliaby HMBC techniques.

Published
1991
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32. Formation of anomeric phosphodiester linkages using H-phosphonate acceptors

Author

Garegg, Per J., Hansson, Jonas, Helland, Anne-Charlotte, and Oscarson, Stefan

Abstract

A new way of constructing anomeric glycosyl phosphodiester linkages has been explored. Non-anomeric monosaccharide hydrogen phosphonate monoesters ( 5and 9) have been used as acceptors in couplings using various benzylated galactosyl donors (trichloroacetimidate, thioglycoside, bromo and chloro sugars, 1–4, 7and 8) and promoters to give, after oxidation, good yields of phosphodiester linked “disaccharides” ( 6and 10), products usually obtained by using an anomeric hydrogen monophosphonate, a hydroxyl acceptor and pivaloyl chloride as coupling reagent.

Published
1999
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35. Conversion of hydroxyl groups into bromo groups in carbohydrates with inversion of configuration

Author

Classon, Björn, Garegg, Per J., and Samuelsson, Bertil

Abstract

A novel reagent system is described for the efficient, one-step transformation of hydroxyl groups in carbohydrates to bromodeoxy groups. The reaction proceeds with inversion of configuration. The reagent system consists of triphenylphosphine, tribromoimidazole, and imidazole in toluene at elevated temperature. The carbohydrate need not be soluble in toluene. The examples given include substitution of isolated primary and secondary hydroxyl groups in otherwise protected carbohydrates as well as disubstitution involving one primary and one secondary position in hexopyranosides. High yields are obtained in the replacement of hydroxyl by bromine in the 2-position of 3,4,6-protected methyl α-D-gluco- and -mannopyranosides.

Published
1981
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37. Effect of Synthetic Disaccharide-Protein Conjugate as an Immunogen in SalmonellaInfection in Mice

Author

Lindberg, A. A., Rosenberg, L. T., Ljunggren, Å., Garegg, P. J., Svensson, S., and Wallin, N.-H.

Abstract

The synthetic disaccharide 3-O-α-tyvelopyranosyl-α-D-mannopyranoside, identical to the O antigen 9 determinant in Salmonella, covalently linked to bovine serum albumin and suspended in Freund complete adjuvant, was used as an immunogen in mice. Antibodies in high titer were formed against the O9 determinant as estimated by a bactericidal assay, whereas only low titers of hemagglutinating antibodies were found. A sensitive in vivo assay demonstrated that in immunized mice, after challenge with two strains of equal virulence but with different O antigens (O9, 12 and O4, 5, 12, respectively), the growth of the strain with the O9 determinant was suppressed in comparison to that with the O4 determinant.

Published
1974
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38. Synthesis of a glucoheptaose and a glucooctaose that elicit phytoalexin accumulation in soybean.

Author

Ossowski, P, Pilotti, A, Garegg, P J, and Lindberg, B

Abstract

The glucoheptaose 1 and the glucooctaose 2 have been synthesized using unambiguous methods. The former is identical with an elicitor-active heptasaccharide obtained from partially hydrolyzed mycelium of Phytophthora megasperma f. sp. glycinea. The octasaccharide is also elicitor active, although to a lesser extent than the heptasaccharide. 1:R = H; 2:R = beta-D-Glcp. (Formula: see text)

Published
1984
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