Jitka Moravcová

One-pot synthesis of 1,2-O-isopropylidene-α-d-xylofuranose

Abstract The title compound 1 was prepared by sulfuric acid-catalyzed acetalation of d -xylose followed by partial hydrolysis with aqueous sodium carbonate added directly to a crude acetalation mixture. The yield of crystalline 1 (mp 42–43°C) was 80%.

Mechanism of Regioselective Mitsunobu Thiofunctionalization of Pentofuranoses

Abstract Triphenylphosphine and diethyl azodicarboxylate react with 1,2-O-isopropylidene-α-D-xylo- (1) and ribofuranose (2) to give six-membered-ring phosphoranes. Xylofuranose 1 undergoes cyclodehydration to produce oxetane 17 in 85% yield, but ribofuranose 2 gives a pyrazolidine derivative 19 in 80% yield. In the presence of 2-mercaptobenzothiazole, the desired 5-S-(benzothiazol-2-yl)-5-thio derivatives 3 and 4 were isolated in 80% yield. 31P NMR examination of this Mitsunobu thiofunctionalization reveals the presence of an alkoxytriphenylphosphonium species as the most stable intermediate which reacts with the thio-nucleophile via SN2 in a rate limiting step.

Synthesis of hapten and conjugates of coumestrol and development of immunoassay

3-O-Carboxymethylcoumestrol was prepared as the hapten for immunoassay by a partial alkylation of coumestrol with ethyl chloroacetate in acetone alkalized with potassium carbonate. 3-O-Ethoxycarbonylmethylcoumestrol was separated by column chromatography and finally was hydrolyzed with formic acid. 1H and 13C NMR data (APT, COSY, HMQC, and HMBC) revealed that the reaction was regioselective, as 3-O-ethoxycarboxymethylcoumestrol was the only monosubstituted derivative. The hapten was then conjugated to bovine serum albumin and used for immunization of rabbits. A radioimmunoassay (RIA) system was established based on the polyclonal antiserum and a 125I-labeled hapten-tyrosine methyl ester conjugate as the radioligand. Parameters of the RIA: sensitivity: 12 pg per tube, 50% intercept: 140 pg per tube, working range: 20-4000 pg per tube. The cross-reactivity of a panel isoflavonoid and lignan phytoestrogens was either negligible (e.g. formononetin 0.07%; biochanin A 0.06%) or not detectable at all. The major immunoreactive peak in HPLC fractions from an alfalfa extract had the same retention time as coumestrol standard and represented 94.8% of the signal. The remaining 5.2% of immunoreactivity was distributed between five minor peaks. We conclude that after the validation for particular matrices, the method will be a useful tool for analysis of coumestrol, especially in low volume and low concentration samples.

Synthesis of 2-fluoro and 4-fluoro galactopyranosyl phosphonate analogues of UDP-Gal

Two novel nonisosteric UDP-Gal analogues, (2-deoxy-2-fluoro- and 4-deoxy-4-fluoro-α-D-galactopyranosyl) phosphonoyl phosphates, were synthesized by optimized multistep procedures starting from 3,4,6-tri-O-benzyl-D-galactal and allyl 2,3,6-tri-O-benzyl-α-D-glucopyranoside, respectively. The key steps were a Michaelis-Arbuzov reaction of respective deoxy-fluoro-D-galactopyranosyl acetate with triethyl phosphite followed by a Moffatt-Khorana coupling reaction with UMP-morpholidate. The structure of all new compounds was confirmed by NMR and mass spectroscopies..

Pig Liver Esterase Catalyzed Hydrolysis of Methyl 2,3-Di-O-Acetyl-5-Deoxy-α- and β-D-Arabinofuranosides

Abstract The regioselectivity of a pig liver esterase (PLE) catalyzed hydrolysis of methyl 2,3-di-O-acetyl-5-deoxy-α-D-arabinofuranoside (1) and methyl 2,3-di-O-acetyl-5-deoxy-β-D-arabinofuranoside (2) was established by GLC. Diacetate 1 gave exclusively methyl 3-O-acetyl-5-deoxy-α-D-arabinofuranoside while diacetate 2 produced both methyl 2-O-acetyl-5-deoxy-β-D-arabinofuranoside and methyl 3-O-acetyl-5-deoxy-β-D-arabinofuranoside which were resistant to subsequent hydrolysis. The Michaelis constants and maximal velocities were determined for 1 and 2. The first-order rate constants were computed for 1, 2, and all corresponding monoacetates. The results were evaluated on the basis of a Joness active-site model for PLE and the additional criteria valid for acetyl esters of pentofuranosides were proposed.

A stereocontrolled synthesis of 3-acetamido-1,3,5-trideoxy- and 1,3,5,6-tetradeoxy-1,5-imino-d-glucitol

3-acetamido-5-amino-3,5,6-trideoxy-D-glucono-1,5-lactam and 3-acetamido-5-amino-3,5-dideoxy-D-glucono-1,5-lactam were synthesized from corresponding 3-acetamido-3-deoxy-beta-D-glucopyranosides in 63% and 35% overall yield, respectively. Acetylation followed by reduction led to the title 3-acetamido-3-deoxy derivatives of both deoxynojirimycin and 1,6-dideoxynojirimycin. The procedure developed is useful for a multi-gram scale.

Enzymic Hydrolysis of Methyl 2,3-O-Acetyl-5-Deoxy-α and β-D-Xylofuranosides - An Active-Site Model of Pig Liver Esterase

Abstract The regioselective enzymic hydrolysis of methyl 2,3-di-O-acetyl-5-deoxy-α-D-xylofuranoside (1) and methyl 2,3-di-O-acetyl-5-deoxy-β-D-xylofuranoside (2) in the presence of pig liver esterase (PLE) was studied by GLC. Diacetate 2 gave exclusively methyl 3-O-acetyl-5-deoxy-β-D-xylofuranoside (6) while diacetate 1 produced both methyl 2-O-acetyl-5-deoxy-α-D-xylofuranoside (3) and methyl 3-O-acetyl-5-deoxy-α-D- xylofuranoside (4) in low yield. At high conversion, methyl 5-deoxy-α-D-xylofuranoside (7) was the only product. The first-order rate constants, Michaelis constants, and maximal velocities were determined for 1, 2, and the monoacetates 3 - 6. The results were interpreted on the basis of a recent active-site model for PLE.

Perfluoroalkylated derivatives of 6-deoxy-6-ethylamino-d-galactose, 1-deoxy-1-methylamino-d-glucitol, and 1-amino-1-deoxy-d-glucitol: syntheses, hemocompatibility, and effect on perfluorocarbon emulsion

N-polyfluoroalkyl derivatives of 6-deoxy-6-ethylamino-1,2;3,4-di-O-isopropylidene-alpha-D-galactopyranose (8-10), 1-deoxy-1-methylamino-D-glucitol (13-15), and 1-amino-1-deoxy-D-glucitol (16-18), all possessing perfluoroalkyl segment, were prepared using nucleophilic epoxide ring opening of 2-[(perfluoroalkyl)methyl]oxiranes 1-3. Co-emulsifying properties and hemolytic activity of the new perfluoroalkylated amphiphiles were tested. Both types of the polyol derivatives 8-10 and 13-18 generally displayed good to excellent co-emulsifying properties on testing on perfluorodecalin/Pluronic F-68 microemulsions. Mono-perfluoroalkylated compounds 8-10 and 13-15 displayed high hemolysis, whereas acyclic bis-perfluoroalkylated compounds 16-18 were non-hemolytic even for short perfluorobutyl segment (16). The properties were generally improving with increasing perfluoroalkyl chain length.