A new, practical, rapid, and high-yielding process for the pressurized hot water extraction (PHWE) of multigram quantities of shikimic acid from star anise (Illicium verum) using an unmodified household espresso machine has been developed. This operationally simple and inexpensive method enables the efficient and straightforward isolation of shikimic acid and the facile preparation of a range of its synthetic derivatives.
Seven new and two known ent-labdane diterpenoids have been isolated from a single plant specimen of Dodonaea viscosa ssp. spatulata, found in Tasmania, Australia. Prior to this study, only seven different labdane diterpenoids had been isolated from D. viscosa. The structures of the natural products were assigned via 1D and 2D NMR spectroscopy and other standard spectroscopic methods. The absolute configuration of three ent-labdane diterpenoids was determined by single-crystal X-ray crystallography of synthetic derivatives. Significantly, the results of this study suggest that the absolute configuration of some known labdane diterpenoids may have been misassigned.
The first total syntheses of the Stemona alkaloids
sessilifoliamides B and D and the second synthesis of sessilifoliamide
C have been completed from a simple pyrrole substrate. The bicyclic
lactam core was prepared on a gram scale via a Brønsted acid
mediated cyclization and controlled oxidation with Dess–Martin
periodinane. This delivered sessilifoliamide C (and its C-11 epimer)
in 24% yield over 11 steps, and sessilifoliamides B and D in 13 and
17 steps, respectively.
Pyrrole, pyrrolidine, and indolizidine alkaloids represent important classes of natural products. Historically, these heterocycles and their derivatives have been the focus of significant interest in organic synthesis. In this report, we review the methods that have been employed to synthesise annulated pyrroles via transformations that include: Friedel-Crafts acylations and alkylations, Michael additions, Heck couplings, hydroarylations, carbenoid insertions, and radical cyclisations.
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