Diketopiperazines from Costa Rican endolichenic fungus Colpoma sp CR1465A

Three new diketopiperazines (1-3), cyclo(L-Pro-D-trans-Hyp) (1), cyclo(L-Pro-D-Glu) (2), and cyclo(D-Pro-D-Glu) (3) and five known diketopiperazines (4-8) were isolated from the endolichenic fungus Colpoma sp. CR1465A identified from the Costa Rican plant Henriettea tuberculosa (Melatomataceae). The structures of the new compounds 1-3 were elucidated using a combination of extensive spectroscopic analyses, including 2D NMR and HR-MS, and their absolute configurations were determined by a combination of NOESY analysis and Marfey's method. Cyclo(L-Pro-D-allo-Thr) (4) was recently isolated from a South China Sea marine sponge Callyspongia sp., but its NMR spectroscopic data were not reported, and cyclo(L-Pro-L-Asp) (5) was previously reported but only as a synthetic product. The NMR data assignments of compounds 4 and 5 are reported for the first time. All of the isolated compounds were tested for antifungal and antimicrobial properties. (C) 2016 Elsevier Ltd. All rights reserved.