ChemInform Abstract: Daphnicyclidins A—H, Novel Hexa‐ or Pentacyclic Alkaloids from Two Species of Daphniphyllum.

Abstract

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Assignment of the absolute configuration of zwitterionic and neutral macropodumines by means of TDDFT CD calculations

“…In addition to some assignments based on chemical correlations and structural similarity arguments, 33,71 a safe configurational assignment had been reported for daphnicyclidin F (5, Chart 2), a compound related to macropodumine C. It was based on the exciton chirality approach, and involved the synthesis of the p-bromobenzoate derivative (5a) and the analysis of its CD spectrum dominated by the exciton coupling between the benzoate and the substituted fulvene chromophore. 72 The CD spectra of other daphnicyclidins (6)(7)(8) and of a related daphnipaxinin (9) had also been reported and employed for configurational assignment. 72,73 The procedure followed in these latter cases lays, however, on a less clear-cut exciton chirality analysis, because the diene and the C¼ ¼O double bonds in 5-9 were incorrectly considered as independent units and their exciton coupling discussed.…”

“…72 The CD spectra of other daphnicyclidins (6)(7)(8) and of a related daphnipaxinin (9) had also been reported and employed for configurational assignment. 72,73 The procedure followed in these latter cases lays, however, on a less clear-cut exciton chirality analysis, because the diene and the C¼ ¼O double bonds in 5-9 were incorrectly considered as independent units and their exciton coupling discussed. A prerequisite of the exciton chirality method is however that the two or more interacting units have negligible molecular overlap, such that conjugation, electron exchange, and resonance phenomena may be excluded.…”

Reprogramming of the biosynthetic network of Daphniphyllum alkaloids into a chemically synthetic network through generalized biomimetic strategies

“…We undertook a systematic analysis of the biogenesis of selected Daphniphyllum alkaloids (1-14, Figures 1A-1D) from the macrodaphniphyllamine, calyciphylline A, daphnilongeranin A, and daphnicyclidin D subfamilies [30][31][32][33][34][35][36][37][38][39][40] , on the basis of their structural relationships and biosynthetic hypotheses. The biosynthetic network of these alkaloids is outlined in Figure 1E.…”

Recent Progress in the Chemistry of Daphniphyllum Alkaloids

“…In 2001, Kobayashi et al 17 reported the isolation of daphnicyclidins A−H from the stems of Daphniphyllum humile and D. teijsmanni. Their structures and stereochemistry were determined on the basis of spectroscopic data and by chemical means and were further confirmed by X-ray crystallography.…”

“…Daphnicyclidin A-type alkaloids possess fused hexa-or pentacyclic structures harboring five stereogenic centers (Figure 9). 17,116 According to the biosynthetic proposal by Kobayashi et al, 17 Tosylation, followed by treatment with TBAF, gave the exocyclic enone via an S N 2′ displacement mode, which upon hydrogenation with Pd-on-carbon gave 206 as an equal mixture of diastereomers. Upon treatment with AcCl in i PrOH, ketone 206 underwent acetal cleavage, followed by iminium ion formation and subsequent Mannich-type addition, to give a separable mixture of 207 and 208.…”