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Configuration, Conformation, and Reactivity of Highly Functionalized Eunicellane Diterpenes Isolated from the Gorgonians Eunicella cavolinii and Eunicella singularis from Marseille
Author(s) -
Mancini Ines,
Guella Graziano,
Zibrowius Helmut,
Pietra Francesco
Publication year - 2000
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/1522-2675(20000705)83:7<1561::aid-hlca1561>3.0.co;2-h
Subject(s) - gorgonian , chemistry , moiety , stereochemistry , cyclohexane , derivative (finance) , ring (chemistry) , reactivity (psychology) , organic chemistry , medicine , alternative medicine , pathology , art , coral , financial economics , economics , visual arts
Eunicellane diterpenes with a C(7)=C(16) ( Δ 7,16 ; see 17 – 19 ), ( Z )‐C(7)=C(8) ((7 Z ) Δ 7,8 ; see 20 – 23 ), and ( Z )‐C(6)=C(7) ((6 Z ) Δ 6,7 ; see 10 ) bond, an uncommon feature in the case of extensive functionalization at the cyclohexane ring and the latter exhibiting uncommon configurations, were isolated from the gorgonian Eunicella cavolinii from Marseille ( Figs. 5 and 2 ). The gorgonian Eunicella singularis (= Eunicella stricta ) from the same area gave (7 Z ) Δ 7,8 , Δ 7,16 , and (6 E ) Δ 6,7 analogs 24 , 25 , and 13 , respectively ( Fig. 5 and Scheme ). The (6 E ) Δ 6,7 moiety of 13 – characterized by a slow 180° conformational flipping ( Fig. 3 ) that results in broadening of NMR signals – makes the macrocycle highly strained. This may explain the spontaneous conversion of 13 to the 6‐methoxy‐7‐hydroxy derivative 14 in the presence of MeOH at −20° in the dark ( Scheme ). The isomeric, deacylated analogue 10 showed only little broadening of NMR signals and proved stable, in accordance with the less strained nature of this compound ( Fig. 4 ).