This derived probably from the lower predicted populations of conformers B and E, in which the ester carbonyl had a different orientation and they had no intense computed ECD transitions at about 225 nm. Thus, the absolute configuration of 7 was determined as (4R,5R,9R,10S). Based on the obtained results, compound 7 was concluded to be a new sesquiterpene derivative featuring a methyl ester moiety in its structure named as abundisporin F. absorption (λmax) at 248 nm suggesting a possible presence of a lactone moiety in its structure. The 13 C NMR data of 8 (Table ) revealed the presence of a ketocarbonyl carbon (δC 196.8, C-7)