DR ANTHONY MELVIN CRASTO,WorldDrugTracker, helping millions, A 90 % paralysed man in action for you, I am suffering from transverse mylitis and bound to a wheel chair, With death on the horizon, nothing will not stop me except God................DR ANTHONY MELVIN CRASTO Ph.D ( ICT, Mumbai) , INDIA 25Yrs Exp. in the feld of Organic Chemistry,Working for GLENMARK GENERICS at Navi Mumbai, INDIA. Serving chemists around the world. Helping them with websites on Chemistry.Million hits on google, world acclamation from industry, academia, drug authorities for websites, blogs and educational contribution

Thursday 13 February 2014

INTERESTING WORLD OF MACROCYCLES

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Graphical abstract: Highly selective one-pot synthesis of H-bonded pentagon-shaped circular aromatic pentamers

Make a macroring in half a day instead of several months. 

INTRODUCTION
Macrocycles are not only esthetically pleasing, but they also can contain multiple functional groups. They are, however, difficult to synthesize. For example, preparing sterically crowded, circularly folded aromatic pentamer 1 required a months-long step-by-step process; and it was obtained in an overall yield of only ≈5%
(Qin, B., et al. Org. Lett. 2008, 10, 5127–5130).
The task is much easier now; it can be accomplished in half a day by using a synthetic route developed by H. Zeng and coauthors at the National University of Singapore, Guang Dong University of Technology (China), and Nanyang Technological University (Singapore).
 One-pot, multi-molecular macrocyclization allows the highly selective preparation of pentagon-shaped circular aromatic pentamers mediated by an inward-pointing continuous hydrogen-bonding network.

Graphical abstract: Highly selective one-pot synthesis of H-bonded pentagon-shaped circular aromatic pentamers

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The protocol is based on a hydrogen-bonding–assisted, one-pot macrocyclization reaction. In the presence of coupling reagent POCl3 and organic base Et3N, 3-amino-2-methoxybenzoic acid (2) undergoes self-amidation under mild conditions to give 1 in a high yield (46%) after a 12-h reaction time. The versatility of this highly selective macrocyclization reaction is illustrated by synthesizing derivatives of 2 with various substituents at the 2- and 5-positions. (Chem. Commun. 2011, 47, 5419–5421;


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ANTHONY MELVIN CRASTO
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