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Methyl 2,3-di-O-benzyl-1-deoxy-1-(prop-2-enyl)-α-D-galactopyranuronate and benzyl 2,3-di-Obenzyl- 1-deoxy-1-(prop-2-enyl)-α-D-galactopyranuronate were prepared as glycosyl acceptors. The glycosyl donors benzyl 4-O-acetyl-2,3-di-O-benzyl-1-(trichloroacetimidoyloxy)-α-Dgalactopyranosyluronate and benzyl 4-O-acetyl-2,3-di-O-benzyl-1-(trichloroacetimidoyloxy)-β- D-galactopyranosyluronate were synthesized in 98% and 76% yields respectively. Disaccharides methyl (methyl 4-O-acetyl-2,3-di-O-benzyl-α/β-D-galactopyranosyluronate)-(1→4)-2,3-di-Obenzyl- 1-deoxy-1-(prop-2-enyl)-α-D-galactopyranuronate and benzyl (benzyl 4-O-acetyl-2,3-di- O-benzyl-α/β-D-galactopyranosyluronate)-(1→4)-2,3-di-O-benzyl-1-deoxy-1-(prop-2-enyl)-α-Dgalactopyranuronate were synthesized in 53% and 44% yields respectively and with moderate stereoselectivity. The synthesis of 1,2-O-acetyl-3,4-di-O-benzyl-L-rhamnopyranose (α/β) and 2- O-acetyl-1-bromo-3,4-di-O-benzyl-α-L-rhamnopyranosyl suitable as glycosyl donors is described. The disaccharide methyl (2-O-acetyl-3,4-di-O-benzyl-α-L-rhamnopyranosyl)-(1→4)- 2,3-di-O-benzyl-1-deoxy-1-(prop-2-enyl)-α-D-galactopyranuronate, and benzyl (2-O-acetyl-3,4- di-O-benzyl-α-L-rhamnopyranosyl)-(1→4)-2,3-di-O-benzyl-1-deoxy-1-(prop-2-enyl)-α-D-galactopyranuronate were obtained in 54% and 56% yield respectively. [ABSTRACT FROM AUTHOR]

Ultrasound irradiation in presence of 20% ZnBr2 effectively promotes regio- and stereo-selective cycloaddition reaction of azomethine ylide with a series of (E)-3-benzylideneindolin-2-ones to afford 3,3'-dispiropyrrolidine bisoxindole derivatives in excellent yields in methanol at room temperature. The factors affecting the cycloaddition reaction, for example solvent, catalyst, ultrasonic irradiation, are examined in detail to find the mildest conditions and highest reaction yields. The structure and stereochemistry of cycloadducts were determined by spectroscopic data and confirmed by X-ray crystallographic analysis. [ABSTRACT FROM AUTHOR]

The article focuses on comparison among carbocations. 9-fluorenycl cation, a member of an antiaromatic intermediates series is obtained by time-related spectroscopy on Ultraviolet (UV) photo-excitation of 9-fluroenyl. 9-Trifluoromethyl-9-fluorenol which incorporates an electron withdrawing substituent was subjected to laser flash photolysis. Photoproduct studies of Methanol showed presence of fluorenyl cation and radical intermediates. A cation discovered from methanol quenching was assigned to corresponding transient obtained from time-resolved spectroscopy in hexafluoroisopropanol (HFIP). The lifetime and methanol quenching rates of these cations are compared to those of 9-methylfluorenyl. Kinetic stability of these cations is then compared to theoretical thermodynamic parameters.