1,5-Anhydro-d-fructose: regioselective acylation with fatty acids

Specific and non-specific enzymes for furanosyl-containing conjugates: biosynthesis, metabolism, and chemo-enzymatic synthesis

There is no doubt now that the synthesis of compounds of varying complexity such as saccharides and derivatives thereof continuously grows with enzymatic methods. This review focuses on recent basic knowledge on enzymes specifically involved in the biosynthesis and degradation of furanosyl-containing polysaccharides and conjugates. Moreover, and when possible, biocatalyzed approaches, alternative to standard synthesis, will be detailed in order to strengthen the high potential of these biocatalysts to go further with the preparation of rare furanosides. Interesting results will be also proposed with chemo-enzymatic processes based on nonfuranosyl-specific enzymes.

Inhibition spectrum studies of microthecin and other anhydrofructose derivatives using selected strains of Gram-positive and -negative bacteria, yeasts and moulds, and investigation of the cytotoxicity of microthecin to malignant blood cell lines

AIMS

To prepare 1,5-anhydro-d-fructose (AF) derivatives, test their microbial inhibition spectrum, and to further examine the most effective AF derivative against Pseudomonas aeruginosa and malignant blood cell lines.

METHODS AND RESULTS

Microthecin and nine other AF derivatives were synthesized from AF. The 10 compounds were tested in vitro against Gram-positive (GP) and Gram-negative (GN) bacteria, yeasts and moulds using a well diffusion method and in a Bioscreen growth analyser. Of the test compounds, microthecin exhibited the most significant antibacterial activity at 100-2000 ppm against both GP and GN bacteria, including Ps. aeruginosa. Further tests with three malignant blood cell lines (Mutu, Ramos, Raji) and one normal cell line indicated that microthecin was a cell toxin, with a cell mortality >85% at 50 ppm. The other nine AF derivatives demonstrated low or no antimicrobial activity.

CONCLUSIONS

Microthecin was active 100-2000 ppm against GP and GN bacteria including Ps. aeruginosa, but was inactive against yeasts and moulds. Microthecin was also a cytotoxin to some mammalian cell lines.

SIGNIFICANCE AND IMPACT OF THE STUDY

Microthecin might have potential for development as a novel drug against Ps. aeruginosa and to target cancer cells. It might also be developed as a food processing aid to control bacterial growth.

Synthesis of Methyl 1-Hydroxy-6-oxo-2-cyclohexenecarboxylate, a Component of Salicortin and Tremulacin, and the Monomer of Idesolide

We have developed a short and practical first synthesis of methyl 1-hydroxy-6-oxo-2-cyclohexenecarboxylate (2), which has been known as a component of salicortin and tremulacin since 1970. Birch reduction of the SEM ether of methyl salicylate followed by oxidation of the intermediate enolate with (-)-camphorsulfonyloxaziridine afforded the SEM enol ether of 2. Hydrolysis of the SEM enol ether afforded 2. We did not observe the dimerization of either racemic or optically enriched 2 to give idesolide (1).

1,5-Anhydro-d-fructose from d-fructose

1,5-anhydro-D-fructose was efficiently prepared from D-fructose via regiospecific 1,5-anhydro ring formation of 2,3-O-isopropylidene-1-O-methyl(tolyl)sulfonyl-D-fructopyranose and subsequent deprotection.

Acylation of different amino derivatives with fatty acids on UL-MFI-type catalysts

Acylation of different amino derivatives (ethanol amine, diethanol amine, N-aminoethylpiperazine) was carried out under green conditions with oleic acid or tail oil fatty acids. The experiments were carried out using as heterogeneous catalysts mesoporous Al-Meso and UL-ZSM-5 with Si/Al ratios between 100 and 20, in the range of the temperatures 80-180 °C without any solvent or in octane or water. The efficiency of the catalysts for the acylation of the investigated substrates appeared to be directly dependent on the Si/Al ratio and the size of the pores. The selectivity toward esters or amides was firstly controlled by temperature, and then by the Si/Al ratios. Additionally, both the conversion and selectivity were controlled by the solvent in which the reaction was carried out. The use of water led mostly to a mixture of esters and amides.

1,5-Anhydro-D-fructose; a versatile chiral building block: biochemistry and chemistry

There is a steadily increasing need to expand sustainable resources, and carbohydrates are anticipated to play an important role in this respect, both for bulk and fine chemical preparation. The enzyme alpha-(1-->4)-glucan lyase degrades starch to 1,5-anhydro-D-fructose. This compound, which has three different functional properties, a prochiral center together with a permanent pyran ring, renders it a potential chiral building block for the synthesis of valuable and potentially biologically active compounds. 1,5-Anhydro-D-fructose is found in natural materials as a degradation product of alpha-(1-->4)-glucans. The occurrence of lyases and the metabolism of 1,5-anhydro-D-fructose are reviewed in the biological part of this article. In the chemical part, the elucidated structure of 1,5-anhydro-D-fructose will be presented together with simple stereoselective conversions into hydroxy/amino 1,5-anhydro hexitols and a nojirimycin analogue. Synthesis of 6-O-acylated derivatives of 1,5-anhydro-D-fructose substituted with long fatty acid residues is carried out using commercially available enzymes. Those reactions lead to compounds with potential emulsifying properties. The use of protected derivatives of 1,5-anhydro-D-fructose for the synthesis of natural products is likewise reviewed. The potential utilization of this chemical building block is far from being exhausted. Since 1,5-anhydro-D-fructose now is accessible in larger amounts through a simple-enzyme catalyzed degradation of starch by alpha-(1-->4)-glucan lyase, the application of 1,5-anhydro-D-fructose may be considered a valuable contribution to the utilization of carbohydrates as the most abundant resource of sustainable raw materials.

Two-step enzymatic synthesis of maltooligosaccharide esters

Glucose and maltose esters were synthesised in organic media by employing a lipase (E.C. 3.1.1.3) from Candida antarctica. In a second reaction step, a transglycosylation catalysed by a cyclodextrin glycosyltransferase (E.C. 2.4.1.19) from either Paenibacillus sp. F8 or Bacillus sp. strain no. 169 (DSM 2518) extended the degree of polymerisation (DP) of the carbohydrate moieties of the carbohydrate esters. The donor substrates used were either a cyclodextrin, a maltooligosaccharide or starch. The highest rate of low DP maltooligosaccharide ester formation was obtained when starch was used as glycosyl donor and caproyl maltose as glycosyl acceptor. The structures of two of the products were identified by 1H and 13C NMR and MALDI-TOF MS as capronate monoesters of maltotriose and maltotetraose, with the ester bond at C-6 of the second glucose unit from the reducing end.