- no.47, pp.25-30, 2005-09-15
Lucilactaene (1), a cell-cycle inhibitor in p53-Transfected cancer, is a synthetically challenging molecule because of its rare hexahydro-3a-hydroxy-5-oxo-2H-furo [3,2-b]pyrrol-6-yl ring system and its substituted and conjugated E,E,E,E,E pentaene moiety, which is unstable to acid, base, and light. Lucilactaene (1), which readily undergoes racemization, has been synthesized for the first time in optically pure form via a biomimetic pathway. The conditions under which racemization occurs were elucidated during this total synthesis. The careful isolation of lucilactaene (1) from both the broth and the mycelia under neutral, nonracemizing conditions demonstrated that the isolable natural product is in fact itself racemic. This total synthesis, which enabled verification of the absolute configuration of lucilactaene (1), has several noteworthy features: All the reactions from NG-391 (2) are mild enough not to affect the labile E,E,E,E,E pentaene moiety; ether formation from 2 to 25 and 28 and the intramolecular Michael reaction from 26 to 27 or from 30 to 31 are both highly stereoselective; the reductive removal of the epoxide with Sml_2 without effecting demethoxylation, andthe deprotection of a hemiaminal under neutral, oxidative conditions via vinyl ether 33 by using a newly developed phenylselenylethyl protecting group, are also useful transformations.