Kalpattu K. Balasubramanian

Abstract: Treatment of tri-O-acetyl- d -glucal 1 with various alcohols and phenols in the presence of InCl3/CH2Cl2 at ambient temperature gave the corresponding alkyl and aryl 2,3-unsaturated glycopyranosides in excellent yields with short reaction times and good anomeric selectivity.

Abstract: Highly deactivated aromatic compounds were smoothly monobrominated by treatment with N-bromosuccinimide (NBS) in concentrated H2SO4 medium affording the corresponding bromo derivatives in good yields. Mild reaction conditions and simple workup provides a practical and commercially viable route for the synthesis of bromo compounds of deactivated aromatics.

Abstract: Treatment of 3,4-dihydro-2 H -pyran 1 with various alcohols 2 – 10 furnished the tetrahydropyranyl ethers 11 – 19 in the presence of 5 M lithium perchlorate in diethyl ether (5 M LPDE), which is essentially a neutral medium.

Abstract: Montmorillonite K10 was found to catalyze, under microwave irradiation, rapid O-glycosidation of 3,4,6-tri-O-acetyl-d-galactal to afford exclusively the alkyl and aryl 2,3-dideoxy-d-threo-hex-2-enopyranosides with very high α-selectivity and without the formation of the 2-deoxy-d-lyxo-hexopyranosides. Under these conditions, 3,4,6-tri-O-acetyl-d-glucal as usual also underwent the Ferrier rearrangement.

Abstract: Naturally occurring carbohydrates and their derivatives have been useful during the last few decades as “chiral pool” constituents in the enantioselective synthesis of biologically active natural and non-natural products. The ready availability of a wide range of carbohydrates in nature and their multichiral architecture, coupled with their well defined stereochemistry, make them attractive starting materials in organic synthesis. The synthesis of key intermediates by incorporation of suitable functional groups onto carbohydrates, which can then be further exploited, has always been a challenging task. In this context, 2-C-formyl glycals, a new class of carbohydrates incorporating an α,β-unsaturated carbonyl system, have recently emerged as potential synthons for numerous organic transformations. Four different syntheses of 2-C-formyl glycals have been reported so far. However, the importance of 2-C-formyl glycals has become well established after our development of a more general, one-step synthesis, employing the well known Vilsmeier−Haack reaction. Synthetic transformations of these 2-C-formyl glycals have resulted in a variety of new compounds of significant synthetic and biological interest. 2-C-Formyl glycals have been shown to be ideal substrates for chemo-, regio- and stereoselective glycosidation, nucleophilic addition/substitution and cycloaddition reactions. The reported syntheses and applications of these important “chiral intermediates” are presented. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)

Abstract: Organ printing can be defined as layer-by-layer additive robotic biofabrication of three-dimensional functional living macrotissues and organ constructs using tissue spheroids as building blocks. The microtissues and tissue spheroids are living materials with certain measurable, evolving and potentially controllable composition, material and biological properties. Closely placed tissue spheroids undergo tissue fusion - a process that represents a fundamental biological and biophysical principle of developmental biology-inspired directed tissue self-assembly. It is possible to engineer small segments of an intraorgan branched vascular tree by using solid and lumenized vascular tissue spheroids. Organ printing could dramatically enhance and transform the field of tissue engineering by enabling large-scale industrial robotic biofabrication of living human organ constructs with "built-in" perfusable intraorgan branched vascular tree. Thus, organ printing is a new emerging enabling technology paradigm which represents a developmental biology-inspired alternative to classic biodegradable solid scaffold-based approaches in tissue engineering.

Abstract: Catalyse par le diaza-1,4bicyclo [2.2.2] octane, la quinuclidine et ses derives, la quinine

Abstract: The [2+2+2] cycloaddition strategy is complementary to the well known Diels-Alder reaction for the generation of polycyclic compounds. This [2+2+2] approach is atom-economical and, with the availability of new catalysts to effect the [2+2+2] cycloaddition reaction, synthesis of a wide variety of highly functionalized polycycles is possible. This review deals with some recent advances relating to [2+2+2] cycloaddition reactions involving the syntheses both of polycycles and of heterocycles. More specifically, syntheses of various biologically active molecules, unusual amino acids, and theoretically interesting molecules are described. An attempt has also been made to give an overview of recent advances in the achievement of chemo-, regio-, and stereoselectivity in cyclotrimerization reactions.

Abstract: This work was supported by the Foundation for Science and Technology (FCT), Portugal (projects PTDC/QUI-QUI/113687/2009 and PEst-C/QUI/UI0081/2013). A.G. (SFRH/BD/43531/2008) and M.J.M. (SFRH/BD/61262/2009) thank FCT for grants.