Potent cytotoxic metabolites from a Leptosphaeria species. Structure determination and conformational analysis

Residual Dipolar Coupling Enhanced NMR Spectroscopy and Chiroptics: A Powerful Combination for the Complete Elucidation of Symmetrical Small Molecules

“…In fact, a similar ECD spectrum, but with inverted sign, was reported by Snyder et al for WIN-64821 (1), with an (R)-C3 configuration, [4] and a similar tendency was observed for leptosin derivatives. [14] Note that in contrast to RDC analysis, which can easily distinguish anti and syn C3-C3' rotamers, this distinction is not possible for ECD spectroscopy analysis, since TD-DFT computations show similar ECD spectroscopy character for the two conformations (Figure 2). This clearly demonstrates the irreplaceable role of RDCs in the conformational and configurational analysis of the homodimeric structures.…”

“…Thus the conformational space of C 2 -like compounds, including the one reported here, differs from C s -like compounds, in which a mixing of + synclinal and Àsynclinal conformation of the phenyl rings has been observed. [14] In the present study, we have measured 10 1 D CH RDCs by using cross-linked polydimethylsiloxane (PDMS) as the alignment medium. [15] Following the molecular mechanics computations-based assumption of a preference for a major anti conformation in 6 (Figure 1), as mentioned above, we performed a RDC analysis separately for each member of the conformational ensembles corresponding to the four trial configurations of 6.…”

Diketopiperazines from Marine Organisms

“…were examined in the P388 lymphocytic leukemia test system. All the compounds exhibited potent cytotoxic activities [57]. Leptosins 41 -44 from the fungus Leptosphaeria sp.…”

Verticillin G, a New Antibacterial Compound from Bionectra byssicola

“…1). Compound 1 is a new derivative of dimeric epidithiodioxopiperazine compounds such as verticillins AϳF [3,4], leptosins AϳC, K, K 1 and K 2 [5,6], Sch52900 [7], chaetosin and chetracin A [8].…”