The [3,5,5,7] tetracyclic skeleton of echinopines has been stereoselectively accessed through a gold(I)-catalyzed alkoxycyclization of cyclopropyl-tethered 1,6-enynes. The key bicyclo[4.2.1]nonane core of the enyne precursors was readily assembled by means of a Co-catalyzed [6 + 2] cycloaddition. Furthermore, the attempted alkoxycyclization of 1,5-enyne substrates revealed an uncovered cyclopro...

[figure: see text] A tandem anionic 5-exo-dig cyclization/Claisen rearrangement sequence was used to effect a facile, "one-pot" conversion of an appropriately substituted 4-alkyn-1-ol to the tetracyclic carbon core structure of phorbol. The synthesis was conducted using readily available nonracemic starting materials to provide the target structure as a single enantiomer in high chemical yield.

Six fluoroquinolones presently in clinical use and four investigational tetracyclic fluoroquinolones were tested for in vitro activity against bloodstream-form Trypanosoma brucei brucei. All compounds had measurable activity, but the tetracyclic analogs were most potent, with 50% effective concentrations in the low micromolar range. In general, trypanosomes were more susceptible than L1210 leuk...

A concise and stereoselective construction of the tetracyclic core of lycorine-type alkaloids and the formal synthesis of α-lycorane has been achieved. The feature of the current method is the employment of a bifunctional thiourea-catalyzed cascade reaction as a powerful tool to construct the skeleton of the natural product, which is a challenging yet very rarely explored strategy. As a result,...

Recently, Uncaria tomentosa (Willd.) D.C. has become known as a healing plant with an ethnomedicinal background. There have been several reports on its constituents, in particular, oxindole alkaloids. It was found that 2 chemotypes of Uncaria tomentosa with different alkaloid patterns occur in nature. The roots of one type contain pentacyclic oxindoles and the other contains tetracyclic oxindol...

SSRIs are chemically distinct from traditional antidepressants such as tricyclic, tetracyclic, and monoamine oxidase inhibitors, but they share the same mechanism of action in that selectively potently inhibit serotonin neuronal reuptake while having no or very little effect on norepinephrine, acetylcholine, histamine reuptake. As a result, when compared to other tricyclic tetracyclic antidepre...

The novel 3H-spiro[1-benzofuran-2-cyclopentan]-3-one skeleton has been made accessible by different routes. One- and two-step protocols lead to tricyclic and tetracyclic benzofuranones 2 and 3, respectively. A four-step synthesis to spirocompound 4 is described. The novel spirocyclic benzofuranones display modest to no inhibition of the human peptidyl prolyl cis/trans isomerase Pin1.

A rapid assembly of the tetracyclic core of FD-838, featuring a catalytic asymmetric Stetter reaction, is described.

A highly convergent, enantioselective total synthesis of brevetoxin A is reported. The development of a [X+2+X] Horner-Wadsworth-Emmons/cyclodehydration/reductive etherification convergent coupling strategy allowed a unified approach to the synthesis of two advanced tetracyclic fragments from four cyclic ether subunits. The Horner-Wittig coupling of the two tetracyclic fragments provided substr...

The application of a Pummerer-initiated tandem reaction cascade leads to the highly stereoselective formation of the tetracyclic core of Nakadomarin A.