Yuan-xun Wang

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08 Apr 00:20

[ASAP] Design, Synthesis, and Pharmacokinetic Evaluation of Phosphate and Amino Acid Ester Prodrugs for Improving the Oral Bioavailability of the HIV-1 Protease Inhibitor Atazanavir

by Murugaiah A. M. Subbaiah, Sandhya Mandlekar, Sridhar Desikan, Thangeswaran Ramar, Lakshumanan Subramani, Mathiazhagan Annadurai, Salil D. Desai, Sarmistha Sinha, Susan M. Jenkins, Mark R. Krystal, Murali Subramanian, Srikanth Sridhar, Shweta Padmanabhan, Priyadeep Bhutani, Rambabu Arla, Shashyendra Singh, Jaydeep Sinha, Megha Thakur, John F. Kadow, Nicholas A. Meanwell

TOC Graphic

Journal of Medicinal Chemistry
DOI: 10.1021/acs.jmedchem.9b00002
26 Jun 05:11

Structure of Amorphous Selenium by 2D 77Se NMR Spectroscopy: An End to the Dilemma of Chain versus Ring

by Maxwell Marple, Jackson Badger, Ivan Hung, Zhehong Gan, Kirill Kovnir, Sabyasachi Sen

Abstract

Amorphous selenium, owing to its tremendous technological importance and perhaps to its chemical simplicity, has been studied for nearly a century and yet an unequivocal structural description of this material remains lacking to date. The primary controversy regarding the structure of amorphous Se relates to the relative fraction of Se atoms residing in inline image chains versus in Se8 rings. Herein we present the results of a two-dimensional solid-state 77Se nuclear magnetic resonance (NMR) spectroscopic study of the chain and ring crystalline allotropes of Se as well as of amorphous Se to unequivocally demonstrate that 1) the Se8 rings and the inline image chains are characterized by their unique 77Se NMR signatures and 2) the structure of amorphous Se consists exclusively of inline image chains.

Thumbnail image of graphical abstract

Se-ing is believing: Amorphous selenium has been studied for nearly a century and yet an unequivocal structural description of it is lacking. The main controversy regarding the structure relates to the fraction of Se atoms residing in inline image chains versus in Se8 rings. 77Se MATPASS/CPMG NMR spectroscopy distinguishes the Se ring and chain environments and shows the structure consists exclusively of inline image chains.