First studies directed towards the diastereoselective synthesis of the BCD tricyclic core of brownin F

Abstract

The BCD tricyclic core of brownin F was prepared in eight synthetic operations for the first time. Our synthesis features a diastereo-, chemo-and regioselective intramolecular [3 + 2] cycloaddition between a cyclic carbonyl ylide and a γ-alkylidenebutenolide.

Oxidopyrylium [5+2] cycloaddition chemistry: Historical perspective and recent advances (2008–2018)

“…Chouraqui and Commeiras recently demonstrated that spirocycles reminiscent of those found in the natural product brownin F could be rapidly accessed by oxidopyrylium cycloaddition chemistry (Scheme 53). 101 Brownin F was isolated in 1994 by Ohmoto from the wood of Harrisonia brownii , 102 and no total synthesis currently exists.…”

Oxidopyrylium-Alkene [5 + 2] Cycloaddition Conjugate Addition Cascade (C3) Sequences: Scope, Limitation, and Computational Investigations

“…The resulting solution was stirred for 30 min at ambient temperature, diluted with anhydrous Et 2 O (34 mL), and cooled to 0 °C. Aldehyde 1b (4.29 g, 17.9 mmol, 1.0 equiv) was added dropwise and the resulting solution was allowed to stir at 23 °C for 1 h at which point the reaction was quenched with sat. aq.…”

“…8 Our initial investigations were sparked by the relative ease of separation of diastereomers (i.e., anti vs syn), straightforward differentiation utilizing 1 H NMR analysis (i.e., diagnostic protons α to ketone), and differing reactivity of each (vide infra). 13 A similar sequence was followed with 2,5disubstituted furan 1b 16 to give acetoxypyranone 2b (eq 2). Construction of substrates with heteroatom-containing tethers (i.e., oxygen 2c and nitrogen 2d) required alternative procedures.…”

The Achmatowicz Rearrangement – Oxidative Ring Expansion of Furfuryl Alcohols

“…In this context, the Lefebvre-type ring expansion of furyl alcohols was combined with pyrylium-alkene cycloadditions and applied in total synthesis routes towards complex natural products. [66][67][68] In 2010, the utility of this strategy was demonstrated by Nicolaou, Chen and co-workers who exploited an Achmatowicz/cycloaddition approach in the assembly of the bicyclic core structure of the sesquiterpenoid englerin A (Scheme 18…”