H. Abdel Hamid

Synthesis of Interglycosidically S‐Linked 1‐Thio‐Oligosaccharides Under Microwave Irradiation*

Microwave irradiation (MWI) has accelerated the synthesis of S‐(2,3,4,6‐tetra‐O‐acetyl‐β‐D‐glucopyranosyl)thiouronium bromide (2a), whose reaction with 2,3,4,6‐tetra‐O‐acetyl‐α‐D‐glucopyranosyl bromide (1a) in the presence of Et3N afforded stereoselectively the acetylated β,β‐1‐thiotrehalose 4a. Similarly, the respective D‐galactopyranosyl 4b and 2‐acetylamino‐2‐deoxy‐D‐glucopyranosyl 4c analog as well as 4,4′‐di‐O‐(2,3,4,6‐tetra‐O‐acetyl‐β‐D‐galactopyranosyl) 4d and 4,4′‐di‐O‐(2,3,4,6‐tetra‐O‐acetyl‐α‐D‐glucopyranosyl) 4e derivatives of 2,2′,3,3′,6,6′‐hexa‐O‐acetyl β,β‐1‐thiotrehalose were prepared. Presented at the EUROCARB12, Grenoble, France, 2003, PB 074, 286.

Microwave-Assisted Organic Synthesis of 3-(D-gluco- Pentitol-1-Yl)-1H-1,2,4-Triazole

The condensation of D-glucono- and D-galactono-1,5-lactone and thiocarbohydrazide to give 3-(D-alditol-1-yl)-4-amino-5-mercapto-1,2,4-triazoles 4 and 5 is accelerated by the use of microwave-assisted organic reaction (MAOS). The deamination and dethiolation of compound 4 to give 6 was also accelerated by the use of MAOS. Condensation of 4 and 5 with p-nitrobenzaldehyde afforded Schiff bases 8 and 9 , respectively, within 4 min under microwave irradiation (MWI), whereas with ethyl chloroacetate the thioalkylated products 14 and 15 were obtained in 8 min. The structures of the synthesized compounds were confirmed by 1 H NMR, 2D NMR, and mass spectra.

MICROWAVE IRRADIATION FOR ACCELERATING THE SYNTHESIS OF ACYCLONUCLEOSIDES OF 1,2,4-TRIAZOLE

The 3-(D-alditol-1-yl)-4-amino-5-mercapto-1,2,4-triazoles 4 and 5 can be successfully prepared using microwave irradiation. Condensation of 4 and 5 with p-nitrobenzaldehyde afforded Schiff bases 6 and 7, respectively. Reaction 4 and 5 with ethylchloroacetate gave the corresponding alkylated products 10 and 11. Better yields and much less time were the characteristic features of using the microwave heating over the conventional one. The structure of the prepared compounds was confirmed by 1H-NMR, 2D-NMR and mass spectra.

MAOS of D‐Gluconic Acid, D‐Glucono‐1,4‐ and 1,5‐Lactones, Esters, Hydrazides, and Benzimidazoles Thereof

Microwave‐assisted organic synthesis (MAOS) of D‐gluconic acid can be efficiently done by oxidation of D‐glucose with bromine water, upon irradiation with microwave (MW). It was also used for the conversion of D‐gluconic acid to ethyl D‐gluconate, D‐glucono‐1,4‐ and 1,5‐lactones, gluconyl hydrazide, and gluconyl phenylhydrazide in yields comparable to those obtained by conventional methods, but in much shorter times. A convenient microwave‐mediated condensation of D‐gluconic acid with o‐phenylenediamines provided the respective acyclonucleoside benzimidazole in short time and good yield.

Microwave Irradiation for Accelerating the Synthesis of Thioglycosides

Abstract A simple and efficient procedure for the synthesis of thioglycosides has been achieved from the reaction of glycosylisothiouronium salts with alkyl or heteroaryl halides under microwave irradiation, in much shorter times and in yields comparable with conventional methods.

Synthesis of functionalised derivatives of pentaerythritol

The synthesis of functionalised derivatives of pentaerythritol has been attempted by the reaction of 1 with different aldehydes and nucleophilic reagents; the activity of various derivatives against hepatitis B virus has been studied.

Synthetic Potential Inherent in D-Isoascorbic Acid as a Precursor for Pyridazine and Furo[3,2-c]pyridazine Ring Systems with Two Asymmetric Centers

Reaction of D-erythro-2,3-hexodiulosono-1,4-lactone-2,3-bis(phenylhydrazone) (2) with an iodine, triphenylphosphine and imidazole mixture afforded the furo[3,2-c]pyridazine derivative 11. Condensation of 6-bromo-6-deoxy-D-erythro-2,3-hexodiulosono-1,4-lactone with phenylhydrazine gave the bishydrazones 6, and 8 or the furo[3,2-c]pyridazine (11) depending on the reaction conditions. The lactone ring in 11 could be opened by treatment with alkali to give the pyridazine derivative 9. Lactonization of the later with simultaneous acetylation by acetic anhydride afforded the lactone derivative 14. Alkali treatment of 6 gave the pyrazolindione derivative 13 that gave upon reation with HBr/AcO H the dibromide 15. The assigned structures were based on spectral analysis. The activity of compounds 11 and 14 against hepatitis B virus has been studied.