Synthesis of Cordiaquinones B, C, J, and K on the Basis of a Bioinspired Approach and the Revision of the Relative Stereochemistry of Cordiaquinone C

Abstract

Four members of the cordiaquinone family (cordiaquinones B, C, J, and K) were synthesized on the basis of a bioinspired scenario in five to six steps from trans, trans-farnesol. As key reactions we used the acid-catalyzed cyclization of a suitable epoxy terpenoid and a Diels-Alder reaction between a diene and benzoquinone. The relative stereochemistry of cordiaquinone C is opposite to that reported in the isolation paper and is in agreement with a plausible scenario for the biosynthesis of cordiaquinones from a common (E)-configurated naphthoquinone epoxide precursor. A fast and clean methodology for the synthesis of the naturally occurring (Z)-beta-farnesene from cis-nerolidol is also reported.

Michael acceptor approach to the design of new salvinorin A-based high affinity ligands for the kappa-opioid receptor

“…13 C NMR experiments confirmed the C-2′ and C-4′ methylene carbons at δ 43.20 and 115.17, and the C-3′ methyl carbon at δ 22.46. The formation of conjugated and non-conjugated isomers in esterification of alcohols with 3,3- dimethylacryloyl chloride in the presence of triethylamine was observed earlier [23, 24]. The elimination-addition and competitive substitution mechanisms are responsible for the formation of both isomers.…”

Harnessing enzyme plasticity for the synthesis of oxygenated sesquiterpenoids

“…The identity of the minor product (15%) was confirmed as ( E )-8-methoxy-β-farnesene ( 21 ) by GC co-elution and comparison of its mass spectrum with an authentic sample prepared by exposing ( E )-β-farnesene synthase to diphosphate 11 (Supporting Information File 1). Further support for the structure of the minor product came from the excellent agreement of the diagnostic 1 H NMR signals of 21 (H1 (δ H = 5.25, d, J H,H = 17.5 Hz), H1’ (δ H = 5.06, d, J H,H = 11.0 Hz), H2 (δ H = 6.38, dd, J H,H = 17.5 and 11.0 Hz), H15 (δ H = 5.02, s), H15’ (δ H = 5.00, s)) with those reported for the parent sesquiterpene ( E )-β-farnesene (Supporting Information File 1) [37]. The proton on C6 (δ H = 5.34, br, t) resonates further downfield for 21 compared to the corresponding proton of ( E )-β-farnesene (δ H = 5.17, t, J H,H = 7.0 Hz) due to the presence of the methoxy group two carbon atoms away.…”

Michael Acceptor Approach to the Design of New Salvinorin A- Based High Affinity Ligands to the Kappa-Opioid Receptor

“…13 C NMR experiments confirmed the C-2′ and C-4′ methylene carbons at δ 43.20 and 115.17, and the C-3′ methyl carbon at δ 22.46. The formation of conjugated and non-conjugated isomers in esterification of alcohols with 3,3-dimethylacryloyl chloride in the presence of triethylamine was observed earlier [23,24]. The elimination-addition and competitive substitution mechanisms are responsible for the formation of both isomers.…”