The enantioselective total syntheses of (+)-7-oxohinokinin, (+)-7-oxoarcitin, (+)-conicaol B and (-)-isopolygamain

A flexible approach to C7 keto dibenzyl butyrolactone lignans was developed and the synthesis of several natural products and their related derivatives is described herein. The developed pathway proceeds through enantioenriched β-substituted butyrolactones, from which facile aldol addition and subsequent oxidation affords the desired benzylic ketone moiety. This methodology was used to complete the first enantioselective total syntheses of three natural products, (+)-7-oxohinokinin, (+)-7-oxoarcitin and (+)-conicaol B, and a further five analogues. The utility of this method was further demonstrated through a 1-2 step modification to access another class of natural product, aryltetralin lignans, allowing the asymmetric total synthesis of (-)-isopolygamain and a polygamain derivative. Anti-proliferative testing determined (-)-isopolygamain was the most active of the compounds prepared, with IC₅₀ values of 2.95 ± 0.61 μM and 4.65 ± 0.68 μM against MDA-MB-231 (triple negative breast cancer) and HCT-116 (colon cancer) cell lines, respectively.

Synthesis of Oxazino[4,3-a]indoles and biological applications

This review brings together the various pathways to the oxazino[4,3-a]indole motif over the last decades. Representative examples showing the scope of these processes will illustrate the synthetic pathways and the biological activity of the synthesized oxazinoindoles will be mentioned wherever possible.

Constituents of Bupleurum praealtum and Bupleurum veronense with Potential Immunomodulatory Activity

In this investigation, chromatographic separations of the diethyl ether extracts of two European annual Bupleurum taxa, B. praealtum and B. veronense, yielded nine new natural products, namely, a series of esters of stereoisomeric tetradeca-5,7,9,11-tetraen-1-ols (1-4 and 8), a tetra-unsaturated γ-tetradecalactone (5), a dibenzylbutyrolactone lignan (7-oxoarcitin, 6), a falcarinol-related 17-membered macrolide (7) possessing a conjugated diyne-system, and an acylphloroglucinol derivative (9). All these new compounds were fully characterized by NMR, IR, UV, MS, and optical rotation measurement, including ¹H NMR full spin spectral simulation, whereas the absolute configurations of 1, 5, and 9 were determined via chemical correlations and NMR analysis of Mosher esters. The in vitro potential immunomodulatory activities of 1, 4, 5, and (+)-arcitin were assessed by determining their effects on the functional properties of isolated rat splenocytes and peritoneal macrophages. The results obtained support the known immunomodulatory ethnomedicinal usage of Bupleurum species.

Gold(I)-catalyzed synthesis of γ-vinylbutyrolactones by intramolecular oxaallylic alkylation with alcohols

Gold(I)-N-heterocyclic carbene (NHC) complexes proved to be a reliable catalytic system for the direct synthesis of functionalized γ-vinylbutyrolactones by intramolecular oxaallylic alkylation with primary alcohols. Good isolated chemical yields were obtained for a range of malonyl and acetate derivatives. The good performance in reagent-grade solvents and the functional group/moisture tolerance make this catalytic process a promising route for the synthesis of architecturally complex polycyclic structures.