開催日: 2017/09/20 - 2017/09/22
Two new cyclopentadecane antibiotics, named mangromicins A and B, were separated out from the culture broth of Lechevalieria aerocolonigenes K10-0216. The chemical structures of the two novel compounds were elucidated by instrumental analyses, including various NMR, MS and X-ray crystallography. Mangromicins A and B consist of cyclopentadecane skeletons with a tetrahydrofuran unit and a 5,6-dihydro-4-hydroxy-2-pyrone moiety. Mangromicins A and B showed in vitro antitrypanosomal activity with IC50 values of 2.4 and 43.4 μg/ml, respectively. An enantioselective total synthesis of (+)-mangromicin A has also been accomplished. The tetrahydrofuran ring of mangromicin A, possessing a tetrasubstituted carbon center, was constructed by Mukaiyama-type vinylogous alkylation via a cyclic oxocarbenium intermediate derived from a γ-hydroxy ketone with ideal stereoselectivity, and the 4-hydroxydihydropyrone scaffold was generated via Dieckmann condensation at a late stage of the total synthesis. The reliable asymmetric synthesis of (+)-mangromicin A has revealed the absolute configuration of naturally occurring mangromicin A.