Stevioside was subjected to 1,4-intermolecular transglycosylation using beta-cyclodextrin glucanotransferase (beta-CGtase) produced from an alkalophilic strain of Bacillus firmus. The reaction was carried out by traditional, ultrasound-assisted and microwave-assisted techniques. Reaction under microwave conditions was faster and was completed in 1 min yielding two 1,4 transglycosylated products, 4'-O-alpha-D: -glycosyl stevioside (I) and 4''-O-alpha-D: -maltosyl stevioside (II) in 66% and 24%, respectively. The optimum transglycosylation occurred by using stevioside (1.24 mmol), beta-CD (1.76 mmol) and beta-CGtase (2 U/g) under microwave assisted reaction (MAR) in 5 ml sodium phosphate buffer (pH 7) at 50 degrees C and 80 W power. MAR is therefore potentially a useful and economical method for faster transglycosylation of stevioside.
Solid‐supported nano‐ and microparticles of rhodium(0) (SS‐Rh) were prepared and applied as a ligand free heterogeneous catalyst for Suzuki–Miyaura cross‐coupling reaction with wide range of substrate scope. A hitherto unknown Rh‐catalyzed Suzuki cross‐coupling reaction of aldehyde and cyanohaloarenes was observed rather than the usual nucleophilic arylation.The catalyst can be removed by simple filtration and recycled upto twelve runs without any deterioration of activity.
Novel classes of b-enaminoesters were synthesized using our newly described ethyl-3-(2,4-dioxocyclohexyl)propanoate molecule (1) under solvent and catalyst free microwave assisted conditions. No work-up procedure, milder reaction conditions, wide substrate scope and high yields add extra importance to this method and open up the scope for acridinediones as well as peptidomimetic molecule synthesis.
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