Beilstein J. Org. Chem.2016,12, 2523–2534, doi:10.3762/bjoc.12.247
and TDDFT–ECD calculations. The synthesized flavonoidalkaloids were further characterized by physicochemical and in vitro pharmacological studies.
Keywords: absolute configuration; Dracocephalum rupestre; dracocephins A–B; ECD calculation; flavonoidalkaloids; HPLC–ECD; Introduction
Flavonoid
cyclization of the Strecker aldehyde 5 yields the acylaminocarbinol intermediate 6, which readily loses water on protonation, resulting in the N-acyliminium ion 7a/b, a strong electrophilic reagent.
Results and Discussion
The aim of our work was to synthesize the natural flavonoidalkaloids 2a–d and 3a–d in a
and B showed good agreement with those of the isolated flavonoidalkaloids [2]. Similarly to the natural route, no diastereoselectivity occurred in this sequence, as proven by the separation of the stereoisomers by chiral HPLC and by the integration or deconvolution of NMR signals of Hy-3 recorded in
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Graphical Abstract
Figure 1:
Structures of (±)-naringenin, (±)-dracocephins A1–A4 and B1–B4 with the indication of the absolute ...