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Absolute structural elucidation of natural products—A focus on quantum‐mechanical calculations of solid‐state CD spectra
Author(s) -
Pescitelli Gennaro,
Kurtán Tibor,
Flörke Ulrich,
Krohn Karsten
Publication year - 2009
Publication title -
chirality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.43
H-Index - 77
eISSN - 1520-636X
pISSN - 0899-0042
DOI - 10.1002/chir.20795
Subject(s) - chemistry , time dependent density functional theory , circular dichroism , spectral line , context (archaeology) , chirality (physics) , quantum , computational chemistry , chemical physics , crystallography , density functional theory , quantum mechanics , physics , chiral symmetry , paleontology , nambu–jona lasinio model , biology , quark
In this review article we examine state‐of‐the‐art techniques for the structural elucidation of organic compounds isolated from natural sources. In particular, we focus on the determination of absolute configuration (AC), perhaps the most challenging but inevitable step in the whole process, especially when newly isolated compounds are screened for biological activity. Among the many methods employed for AC assignment that we review, special attention is paid to electronic circular dichroism (CD) and to the modern tools available for quantum‐mechanics CD predictions, including TDDFT. In this context, we stress that conformational flexibility often poses a limit to practical CD calculations of solution CD spectra. Many crystalline natural products suitable for X‐ray analysis do not contain heavy atoms for a confidential AC assignment by resonant scattering. However, their CD spectra can be recorded in the solid state, for example with the KCl pellet technique, and analyzed possibly by nonempirical means to provide stereochemical information. In particular, solid‐state CD spectra can be compared with those calculated with TDDFT or other high‐level methods, using the X‐ray geometry as input. The solid‐state CD/TDDFT approach, described in detail, represents a quick and reliable tool for AC assignment of natural products. Chirality 21:E181–E201, 2009. © 2009 Wiley‐Liss, Inc.