A Diels–Alder/Retro‐Diels–Alder Approach for the Enantioselective Synthesis of Microbial Butenolides

Abstract

Several volatile lactones have been identified from the endophytic fungus Geniculosporium sp. isolated from the rockrose Cistus monspeliensis, commonly known as Montpelier cistus. The fungal volatiles were collected from agar‐plate cultures by using a closed‐loop stripping apparatus and the headspace extracts were analysed by GC–MS. Structures for these lactones were proposed from their mass spectral data. The suggested structures were verified by synthesis of reference compounds through a Diels–Alder/retro‐Diels–Alder approach. This synthetic method was also successfully applied in the synthesis of butenolides that are signalling molecules from streptomycetes. For the enantioselective synthesis of these butenolides a modified route including an enantioselective Diels–Alder reaction was used.

Characterization of novel isobenzofuranones by DFT calculations and 2D NMR analysis

“…Although these compounds have been previously described in the literature, their NMR spectra have not been fully assigned . Therefore, the complete structural elucidations of 2 and 3 have been carried out in the present work.…”

Volatiles from the ascomyceteDaldinia cf. childiae(Hypoxylaceae), originating from China

“…1A) is 2-butyl-3-methylbut-2-en-4-olide (1) from Hypoxylon serpens (currently valid name: Nemania serpens), 3 a compound that was also found in an endophytic isolate assigned to the genus Geniculosporium (the asexual state of Nemania). 4 In N. serpens it is accompanied by its isomer 2-butyl-3-methylenebutan-4-olide (2). 3 With respect to terpenes, 1,8-cineol (3) has been reported from endophytic species of the genus Hypoxylon, 5,6 and the monoterpene synthase for this compound has recently been identified.…”

Continuous-flow retro-Diels–Alder reaction: an efficient method for the preparation of pyrimidinone derivatives

“…The rDA process is an efficient technique for the introduction of a double bond into a heterocyclic skeleton [ 26 ] as well as for the enantiodivergent [ 27 ] and the enantiocontrolled [ 28 ] syntheses of heterocyclic compounds. The rDA products can be gained, due to a thermal [4 + 2]-cycloreversion, by distillation under reduced pressure [ 29 ], boiling in solvent [ 30 – 31 ], and applying microwave irradiation [ 32 – 35 ] or flash vacuum pyrolysis [ 35 – 36 ]. rDA reactions under mild conditions have been widely examined and discussed for the laboratory preparation of heteromonocycles or condensed-ring heterocycles [ 37 – 40 ].…”