The reliability and utility of high reported specific rotations: reports and predictions of molecules with extremely high specific rotations, and high specific rotations suggest revision of the structures of huperzines E′ and F′

Abstract

A search of the literature for all compounds with [α]D>1000 found 13 molecules with reliably determined specific rotations in excess of 6500, as judged by comparison with DFT-calculated values of [α]D for the same compounds, with a maximum [α]D −11,560 for a decacyclic helicene quinone. Several reports of [α]Ds ranging from 10,000 to 44,000 were judged to be spurious. On the basis of similar computational studies, several molecules are proposed that should have very high [α]Ds but relatively modest visible absorptions, unlike the current record holders, which have strong absorption near the sodium D line. In addition, the search found two natural products, huperzines E′ and F′, that have large reported [α]Ds (−4750 and −3182, respectively), that are inconsistent with their structures. However, computational studies found epimers of the reported structures that possess [α]Ds consistent with the reported chiroptical data.

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