Ketene Acetal and Spiroacetal Constituents of the Marine Fungus Aigialus parvus BCC 5311

Abstract

Aigialone (1) and aigialospirol (2), two structurally unique compounds, were isolated from the mangrove fungus Aigialus parvus BCC 5311. The structure of the new ketene acetal 1 was elucidated by spectral analysis, and its relative stereochemistry was determined by X-ray crystallography. The stereochemistry of aigialospirol (2), elucidated by NMR spectral analysis, suggested that this compound is possibly derived from hypothemycin (3), a metabolite previously isolated from this same fungus.

Three xanthones from a marine-derived mangrove endophytic fungus

“…Their structures were elucidated as sterigmatocystin (1), dihydrosterigmatocystin (2), and secosterigmatocystin (3) by analysis of spectroscopic data.…”

“…Marine fungus, especially mangrove endophytic fungus, has proved to be an abundant resource for novel natural compounds [1][2][3][4][5][6][7][8][9][10][11][12][13]. During our screening for novel structures from marine-derived mangrove endophytic fungus from the South China Sea, a fungal strain (isolate 1850) was found to produce three xanthones (1-3).…”

Two remarkable epimerizations imperative for the success of an asymmetric total synthesis of (+)-aigialospirol

“…Combining the prevalence of spiroketals in biologically active natural products1,2 and the power of RCM has rendered this a fundamentally different approach truly significant in natural product synthesis 7,14. More specifically, we became involved with the total synthesis of (+)-aigialospirol [ 4 ]15 to demonstrate a point that the cyclic acetal tethered RCM strategy via 5 can lead to a competitive if not superior total synthesis than the classical spiroketal formation through diol-ketone 6 .…”

“…The isolation of (+)-aigialospirol [ 4 ] was reported by Isaka 15. It was obtained after an extended fermentation of the marine fungus Aigialus parvus BCC 5311 that was found in the mangrove Ascomycete.…”

“…Specifically, 4 is postulated15 to be derived from macro-lactone 8 via two steps, trans-lactonization and spiroketal formation. The macro-lactone 8 can be derived from a hydrative opening of the epoxide in 7 with inversion of stereochemistry at C1’.…”