Regioselective Benzylation of 2-Deoxy-2-Aminosugars Using Crown Ethers: Application to a Shortened Synthesis of Hyaluronic Acid Oligomers.

The combination of benzyl bromide, sodium hydroxide and 15-crown-5 in tetrahydrofuran is shown to be an efficient method for installing benzyl groups at both the 4- and 6-positions regioselectively directly from peracetylated N-trichloroacetyl-protected glucosamine and galactosamine. Application of this benzylation strategy proved to significantly shorten the synthetic route to hyaluronic acid tetra- and hexamers.

Chemistry and biology of oligovalent ß-(1→2)-linked oligomannosides: new insights into carbohydrate-based adjuvants in immunotherapy.

A series of oligovalent carbohydrate assemblies (ranging from mono- to pentavalent), derived from three structurally different ß-linked or ß-(1→2)-linked mannosides, has been chemically synthesized, and the respective compounds have been biologically evaluated in order to investigate their immunostimulatory properties. The Crich methodology for ß-mannosylation was successfully utilized to introduce the ß-linkages, and a click chemistry protocol was utilized to generate the oligovalent derivatives. A convenient protecting group strategy involving the simultaneous use of both p-methoxybenzyl and benzylidene groups was employed, which allowed a simple and cost-effective global deprotection step. The immunomodulatory properties of the synthesized multivalent mannosides were evaluated by assessing cytokine production in human white blood cell cultures. The Th2-type cytokines interleukin-4 and interleukin-5 (IL-4 and IL-5), the Th1 cytokine interferon-γ (IFN-γ), the Treg cytokine IL-10, and the pro-inflammatory cytokine tumor necrosis factor (TNF) were included in the screening. A single trivalent acetylated mannobiose derivative was identified as a potent inducer of Treg and Th1 immune response, resulting in strong IL-10 and moderate IFN-γ productions dose-dependently, while inducing no Th2 cytokine response. The immunomodulatory properties of this trivalent mannoside were further studied in vitro in allergen (Bet v)-stimulated human peripheral blood mononuclear cell cultures of birch pollen allergic subjects. Stimulation with birch pollen induced strong IL-4 and IL-5 responses, which could be suppressed by the trivalent acetylated mannobiose derivative. The IL-10 response was also suppressed, whereas the production of IFN-γ was strongly enhanced. The results suggest that the identified lead compound has suppressive effects on the Th2-type allergic inflammatory response and shows potential as a possible lead adjuvant for the specific immunotherapy of allergies.

Efficient synthesis of (6-deoxy-glycopyranosid-6-yl) sulfone derivatives and their effect on Ca2+-ATPase.

Synthesis of a series of novel (6-deoxy-glycopyranosid-6-yl) sulfone derivatives has been achieved using a general synthetic strategy. Yields were excellent in every case. The synthetic compounds were evaluated for their biological potential against Ca2+-ATPase, an important enzyme involves in transporting Ca2+ across the cell membranes.

Total synthesis of an antigenic heptasaccharide motif found in the cell-wall lipooligosaccharide of Mycobacterium gordonae strain 989.

An antigenic heptasaccharide motif of the cell-wall glycolipid of Mycobacterium gordonae strain 989 has been synthesized in a linear fashion by using a general glycosylation condition and minimum number of protecting group manipulation. All suitably protected monosaccharide intermediates were prepared from commercially available reducing sugars following some novel methodologies recently developed in our laboratory. Most of the synthetic intermediates were obtained as solid compounds in excellent yields.

First total synthesis of a pentasaccharide repeating unit of the O-antigen of Hafnia alvei PCM 1529.

A pentasaccharide repeating unit of the O-antigen of Hafnia alvei has been synthesized in a concise manner. High yielding glycosylation steps and minimum number of protecting group manipulation steps are the key features of this synthesis. A two-step, one-pot phase transfer oxidation protocol has been applied for the preparation of D-galacturonic acid.