Synthesis of (±)‐Strychnofoline via a Highly Convergent Selective Annulation Reaction

Abstract

Studies aimed at preparing (+/-)-strychnofoline by total synthesis are detailed. The route described makes use of a recently developed MgI(2)-mediated ring-expansion reaction of spiro[cyclopropan-1,3'-oxindole] with a cyclic disubstituted aldimine. The ring-expansion product was formed as a single diastereoisomer in 55 % yield, possessing the same stereochemical pattern found in strychnofoline. In addition, our synthetic effort has led to the development of new reaction methodology to access 3,4-disubstituted cyclic aldimines.

Molecular diversity of spirooxindoles. Synthesis and biological activity

“…They can be further classified into two substructural classes: (1) the tetracyclic secoyohimbane or corynantheidine type (e.g., rhynchophylline 10), and (2) the pentacyclic heteroyohimbane or ajmalicine type (e.g., formosanine 11) [13]. General traditional medicinal uses of Uncaria include treatments for a wide variety of diseases, such as fever, colic, muscular pains, and worm infestations [14][15][16].…”

Diastereoselective Access to Tri‐ and Pentacyclic Spiro‐γ‐lactam‐oxindole Cores through a Tandem Aza‐Michael Initiated Ring Closure Sequence

“…[6] The spiro[pyrrolidin-3,3Ј-oxindole] core is also found in strychnofoline (6), which is isolated from the leaves of Strychnos usambarensis, and inhibits mitosis of cancer cell lines. [7] In addition, javaniside (7), a pentacyclic spirooxindole, has been shown to act as an agent that is capable of Cu 2+ dependant DNA cleavage. [8] One of the challenges in the synthesis of these oxindole alkaloids is the formation of the quaternary spiro tion were usually high and furnished original spiro[oxindole-3,3Ј-γ-lactam] derivatives.…”

Synthesis and reduction reactions of pyridones and 5-acyl-2-methoxypyridines

“…29 This compound was prepared following the general procedure for alkene hydrogenation, using 1-benzyl-6-oxo-1,6-dihydropyridine-3-carboxylic acid, 3a (30 mg, 0.131 mmol) and palladium on carbon (10 % w/w, 13 mg, 1.22 x 10 -2 mmol) in methanol (1 mL 29 This compound was prepared following the general procedure for alkene hydrogenation, using methyl 1-benzyl-6-oxo-1,6-dihydropyridine-3-carboxylate, 3b (100 mg, 0.411 mmol) and palladium on carbon (5 % w/w, 88 mg, 4.13 x 10 -2 mmol) in methanol (1 mL) following a reaction time of 1 d, at 40 °C under a balloon of hydrogen. Following solvent removal and purification by column chromatography (ethyl acetate -hexane 9:1), the product (±)-4b (30 …”