Stereoselective routes to aryl substituted γ-butyrolactones and their application towards the synthesis of highly oxidised furanocembranoids

Abstract

Titanium chelate addition of aryl nucleophiles to cyclopropyl aldehyde 6 followed by a tin-catalyzed one-pot retro-aldol, acetalisation and lactonisation sequence afforded cis and trans c-aryllactone acetals. A c-furyllactone derived by this approach was further transformed in two steps to model compounds for the oxidised northeastern sectors of selected Pseudopterogorgia diterpenoids.Highly substituted g-butyrolactone motifs are profusely present in many synthetic intermediates and biologically active structures.

Catalytic Conversion of Furans and Pyrroles to Natural Products and Analogues Utilizing Donor‐Acceptor Substituted Cyclopropanes as Key Intermediates

“…Given that the sterically bulky, but at the same time, potentially chelating, oxalate ester is located cis to the aldehyde functionality, nucleophile addition can be envisioned, either following the Felkin‐Anh or the Cram Chelate paradigm . Thus, boron trifluoride‐mediated addition of allylsilanes or silylenolethers gives rise to 20 via nucleophile attack on the carbonyl group in conformer 19 from the sterically less hindered side, while nucleophile addition to chelate 21 that is formed with aryl titanium reagents proceeds with opposite face selectivity …”

Asymmetric Synthesis of N,O-Heterobicyclic Octanes and (−)-Geissman–Waiss Lactone

“…As part of an effort to develop efficient synthetic methodologies for the preparation of heterocyclic compounds, , we herein report the synthesis of GWL ( 1 ) via sequential transformations involving oxidative lactonization/lactamization sequences from meso -cyclohexadiene epoxide.…”

“…To the best of our knowledge, the only example known makes use of the Katsuki−Sharpless kinetic resolution of racemic N-benzyloxycarbonyl-3-hydroxy-4-pentenylamine. 19 As part of an effort to develop efficient synthetic methodologies for the preparation of heterocyclic compounds, 28,29 we herein report the synthesis of GWL (1) via sequential transformations involving oxidative lactonization/lactamization sequences from meso-cyclohexadiene epoxide.…”