The leaves of Tillandsia brachycaulos afforded two novel tetracyclic triterpenoids identified as (24S)-24-isopropenyl-29-nor-5alpha-lanosta-7-en-3beta-ol (1) and (24S)-24-isopropenyl-29-nor-5alpha-lanosta-7-en-3-one (2), in addition to the known isopimaric acid (3) and chlorogenic acid (4). Their structures were elucidated on the basis of spectral analysis, including homo- and heteronuclear cor...

A reliable synthetic route to fused polycyclic indolines is documented by the development of a stereoselective gold catalyzed cascade cyclization of indole propargylic alcohols.

The fawcettimine class of Lycopodium alkaloids consists of over 60 natural products. Typically, these tetracyclic compounds contain a single quaternary carbon center and are derived biosynthetically from the lycopodane core through an oxidative rearrangement reaction. In 1959, the first member of this class, fawcettimine (1), was isolated by Burnell in the Blue Mountain Range of Jamaica. Inubus...

An asymmetric annulation reaction of γ-butenolides and cyclic 1-azadienes containing a 1,2-benzoisothiazole-1,1-dioxide motif has been studied, proceeding in a tandem Michael addition-aza-Michael addition sequence. Endo-type cycloadducts bearing fused tetracyclic skeletons were isolated in fair yields and with high enantioselectivity (up to >99% ee) under the catalysis of modified cinchona alka...

Paniculatine 1, magnellanine 2. and magnellaninone 3 are three structurally similar tetracyclic alkaloids isolated and characterized by Castillo in 1976.3 Despite their unusual and interesting structures, there has been a paucity of effort directed toward the synthesis of this class of alkaloids.3 We report hem our studies on the synthesis and characterization of two tricyclic intermediates whi...

Mn(III)-based oxidative free-radical cyclization of an unsaturated beta-keto ester containing a pyridine ring as radical trap has been studied. This intramolecular reaction of nucleophilic carbon-centered radicals with the pyridine ring leads to the stereospecific construction of a tetracyclic compound in which five chiral centers are created in one pot. This synthetic approach represents the f...

Lycoposerramine A (1) is a pentacyclic alkaloid isolated in 2001 by Takayama and co-workers. A concise synthesis of a model compound 8 for the tetracyclic core of this natural product is described. Key steps include the desymmetrising free-radical cyclisation of compound 7 to give compound 18 and spirocyclisation of compound 26 to give compound 8. Earlier approaches using a novel high-yielding ...

A stereoselective synthesis of the BCDE fragment of brevetoxin A has been completed. anti-Glycolate aldol, glycolate alkylation, and ring-closing metathesis reactions were employed as key bond-forming events. A convergent assembly strategy was employed that relied on a Horner-Wadsworth-Emmons union of two complex fragments. Subsequent cyclization and dehydration led to efficient generation of a...

A chemical analysis of the diterpene hydrocarbons produced by fusicoccin-producing fungus Phomopsis amygdali F6 identified five phyllocladene-related tri- and tetracyclic diterpene hydrocarbons. The presence of (+)-phyllocladene, (--)-sandaracopimaradiene, (+)-isopimara-8,15-diene, and (+)-pimara-8(14),15-diene in the fungus was demonstrated by GC-MS, 1H-NMR, and [alpha]D measurements. (+)-Kaur...

A series of functionalized 2,3-dihydro-1,4-benzoxazines were obtained in moderate to excellent yields via domino [5 + 1] annulations of 2-halo-1,3-dicarbonyl compounds 2 with imines 1 under mild conditions and the application of this method in the synthesis of bioactive analogues, such as functionalized tetracyclic-1,4-benzoxazines which contain two new heterocyclic rings and one quaternary car...