The determination of absolute structure. II. Absolute configurations from the Cambridge Crystallographic Data Centre files for 1982

Abstract

A survey of 102 structures flagged with 'absolute configuration' in the Cambridge Crystallographic Data Centre files for 1982 reveals many unsatisfactory features in the original publications. These are associated with data collection (lack of Friedel opposites and of absorption corrections), misinterpretation of the term 'absolute configuration' (claimed for achiral molecules and space groups), methods used to determine absolute configuration (over-optimistic interpretation of discriminatory tests) and presentation of results (little experimental detail, no prominent statement that an absolute configuration was assigned, no clear description of the methods used). Some confusion arises because of unintentional flagging of absolute configurations determined by solely chemical means.would today be either obviously correct or, in suspicious cases, easy to check. It therefore seemed worth while to inspect more recent reports of absolute structures to see if the situation had improved. This paper reviews such reports from the year 1982.

Determination of absolute structure using Bayesian statistics on Bijvoet differences

“…This difference in intensity (the 'Bijvoet difference') depends both on the atom types present in the molecule and the wavelength of the radiation used (Flack & Shmueli, 2007). The concept of 'absolute configuration' has since been generalized to 'absolute structure' to include cases where the polarity of the structure rather than the absolute configuration is determined (Jones, 1984;Glazer & Stadnicka, 1989).…”

Absolute structural elucidation of natural products—A focus on quantum‐mechanical calculations of solid‐state CD spectra

“…Finally, wrong determination and/or consideration of space group and resulting symmetry information, although rare, may lead to misinterpreted results 29. In 1982, a detailed inspection by Jones30 of the then 102 entries in the Cambridge Structural Database31, 32 bearing the “absolute configuration” flag revealed “many unsatisfactory features in the original publications”. The situation of today with 6982 correspondingly flagged structures has possibly improved, but paying attention to Jones' comments30, 33 is still strongly recommended.…”

“…The February 2009 version of the CSD Cambridge database31, 32 comprises about 7000 structures in chiral space groups that are flagged with “absolute configuration” but only 523 of these consist of H, C, O, and N atoms, and 40 of H, C, O, N, F (8% overall). The problems concerning correct assignment of absolute configuration (or absolute structure) by X‐ray diffraction especially in these difficult cases30, 33 have been already outlined (section “Assign Absolute Configurations”). Considering that most interesting biologically active natural compounds contain at least one unsaturation (a chromophoric group), there is much space available for application of the solid‐state CD method for assigning ACs.…”