Plakilactones G and H from a marine sponge. Stereochemical determination of highly flexible systems by quantitative NMR-derived interproton distances combined with quantum mechanical calculations of (13)C chemical shifts.
In this paper the stereostructural investigation of two new oxygenated polyketides, plakilactones G and H, isolated from the marine sponge Plakinastrella mamillaris collected at Fiji Islands, is reported. The stereostructural studies began on plakilactone H by applying an integrated approach of the NOE-based protocol and quantum mechanical calculations of (13)C chemical shifts. In particular, plakilactone H was used as a template to extend the application of NMR-derived interproton distances to a highly flexible molecular system with simultaneous assignment of four non-contiguous stereocenters. Chemical derivatization and quantum mechanical calculations of (13)C on plakilactone G along with a plausible biogenetic interconversion between plakilactone G and plakilactone H allowed us to determine the absolute configuration in this two new oxygenated polyketides.
Dipartimento di Farmacia, Università di Salerno, via Giovanni Paolo II 132, 84084 Fisciano (SA), Italy.
Simone
S
Di Micco
Dipartimento di Farmacia, Università di Napoli "Federico II", via D. Montesano 49, 80131 Napoli, Italy.
Angela
A
Zampella
Dipartimento di Farmacia, Università di Napoli "Federico II", via D. Montesano 49, 80131 Napoli, Italy.
Maria Valeria
MV
D'Auria
Dipartimento di Farmacia, Università di Napoli "Federico II", via D. Montesano 49, 80131 Napoli, Italy.
Carmen
C
Festa
Dipartimento di Farmacia, Università di Napoli "Federico II", via D. Montesano 49, 80131 Napoli, Italy.
Simona
S
De Marino
Dipartimento di Farmacia, Università di Salerno, via Giovanni Paolo II 132, 84084 Fisciano (SA), Italy.
Raffaele
R
Riccio
Department of Chemistry, University of Bristol, Cantocks Close, BS8 1TS Bristol, United Kingdom.
Craig P
CP
Butts
Dipartimento di Farmacia, Università di Salerno, via Giovanni Paolo II 132, 84084 Fisciano (SA), Italy.
Giuseppe
G
Bifulco
DFT; NMR spectroscopy; chemical shift calculations; quantitative NOE; stereochemical determination of flexible systems