On terpenes. CLXXXVIII. Constitution and configuration of pelenolides, a new group of sesquiterpene lactone germacranolides

Sesquiterpene Lactones from Artemisia absinthium. Biotransformation and Rearrangement of the Insect Antifeedant 3α-hydroxypelenolide

“…Indeed, the presence of espeletone (11) in this plant, and its 10, 11-dehydro derivative, indicates that 18 could be an alternative structure. Additional known compounds isolated from A absintium have been the monoterpene (-)-(3S, 5Z)-2,6-dimethylocta-5,7-dien-2,3-diol [2,3,26], the sesquiterpene lactones 3α-hydroxypelenolide (3) [4][5][6], ketopelenolide A (4) [4], ketopelenolide B (5) [4,27], and dihydrocostunolide (6) [27], the diterpene dehydroabietic acid [28], the triterpenes 24methylencycloartanol and its acetate [29], lagerenol and its acetate [30], and cycloart-23(Z)-en-3β,25-diol [31], the acetophenone espeletone (11) [21], a benzofurane derivative (19) [22,32] and the flavones artemetine [33,34] and casticine [35]. We have now assigned the 1 H and 13 C NMR spectra of espeletone (11) (Figures S11 and S12) and of the benzofuran derivative 19 (Figures S15 and S16) using 2D NMR data (Table 1).…”

“…However, the non-volatile constituents of A. absinthium have received little attention. This plant is characterized by its content in the sesquiterpene lactones hydroxypelenolide ( 3 ) and ketopelenolides A and B ( 4 – 5 ) [ 4 , 5 , 6 ]. Additionally, five sesquiterpene lactones, a flavone [ 7 ] and a germacrane lactone artabolide with auxin transport inhibitor properties [ 8 ] have been also reported.…”

“…In this context, Mucor plumbeus, with a broad substrate specificity [11,12], has been used in biotransformations of diterpenes to develop models to explain their hydroxylations [13][14][15][16][17] and for the biotransformation of an africanane sesquiterpene to give epoxy Plants 2021, 10, 891 2 of 14 derivatives with improved insect antifeedants and insecticidal effects [18]. In this work we describe three unknown compounds, the sesquiterpene lactones absilactone (1) and hansonlactone (2) and the acetophenone derivative artenol (12) [4], isolated from A. absinthium var. candial along with several known compounds.…”

“…candial along with several known compounds. Furthermore, 3α-hydroxypelenolide (3), previously known as hydroxypelenolide [4], was biotransformed by Mucor plumbeus to give 1β, 10α-epoxide (9) and a cadinane derivative (10). The latter was formed by an acid rearrangement produced in the culture medium, not by the enzymatic system of the fungus.…”

Crystal structure of hydroxypelenolide p-bromobenzoate

“…Partial formula I has been proposed for hydroxypelenolide, one of three chemically interrelated sesquiterpene lactones isolated from Artemisia absinthium L. 1 To test this proposed formula and to establish the remaining stereochemical features of these substances, the title compound was prepared and subjected to an X-ray study.2 b,R = p-COC6H4Br…”