(+)- and (−)-Pestaloxazine A, a Pair of Antiviral Enantiomeric Alkaloid Dimers with a Symmetric Spiro[oxazinane-piperazinedione] Skeleton from Pestalotiopsis sp.

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Abstract
A pair of new enantiomeric alkaloid dimers, (+)- and (-)-pestaloxazine A (1), with an unprecedented symmetric spiro[oxazinane-piperazinedione] skeleton, consisting of 22 carbons and 12 heteroatoms, were isolated from a Pestalotiopsis sp. fungus derived from a soft coral. Separation of the enantiomeric alkaloid dimers was achieved by chiral HPLC. Their structures including absolute configurations were elucidated on the basis of a comprehensive analysis of their spectroscopic and X-ray diffraction data and CD calculations. (+)-Pestaloxazine A exhibited potent antiviral activity against EV71 with an IC50 value of 14.2 ± 1.3 μM, which was stronger than that of the positive control ribavirin (IC50 = 256.1 ± 15.1 μM).
Funding Information
  • the Science and Technology Development Plan of Shandong Province (2014GSF120004)
  • the Special Foundation for Taishan Scholar Professorship of Shandong Province and UJN (ts20130937)
  • National Natural Science Foundation of China (21102022, 21175057, 21375047, 21377046, 21505051, 21575050, 41130858, 41176121, 41322037)
  • the Science and Technology Plan Project of Jinan (201307010)