A Review on Biological Properties and Synthetic Methodologies of Diarylpentadienones.

Medicinal chemists have continuously shown interest in new curcuminoid derivatives, diarylpentadienones, owing to their enhanced stability feature and easy preparation using a one-pot synthesis. Thus far, methods such as Claisen-Schmidt condensation and Julia- Kocienski olefination have been utilised for the synthesis of these compounds. Diarylpentadienones possess a high potential as a chemical source for designing and developing new and effective drugs for the treatment of diseases, including inflammation, cancer, and malaria. In brief, this review article focuses on the broad pharmacological applications and the summary of the structure-activity relationship of molecules, which can be employed to further explore the structure of diarylpentadienone. The current methodological developments towards the synthesis of diarylpentadienones are also discussed.

Metabolite Characterization and Correlations with Antioxidant and Wound Healing Properties of Oil Palm (Elaeis guineensis Jacq.) Leaflets via 1H-NMR-Based Metabolomics Approach.

Oil palm (Elaeis guineensis Jacq.) leaflets (OPLs) are one of the major agricultural by-products generated from the massive cultivation of Malaysian palm oil. This biomass is also reported to be of potential value based on its health-improving effects. By employing proton nuclear magnetic resonance (1H-NMR) spectroscopy combined with multivariate data analysis (MVDA), the metabolite profile of OPLs was characterized and correlated with their antioxidant and wound healing properties. Principal component analysis (PCA) classified four varieties of extracts, prepared using solvents ranging from polar to medium polarity, into three distinct clusters. Cumulatively, six flavonoids, eight organic acids, four carbohydrates, and an amine were identified from the solvent extracts. The more polar extracts, such as, the ethyl acetate-methanol, absolute methanol, and methanol-water, were richer in phytochemicals. Based on partial least square (PLS) analysis, the constituents in these extracts, such as (+)-catechin, (-)-epicatechin, orientin, isoorientin, vitexin, and isovitexin, were strongly correlated with the measured antioxidant activities, comprising ferric reducing antioxidant power (FRAP), 2,2-diphenyl-1-picrylhydrazyl (DPPH), and nitric oxide (NO) free radical scavenging activities, as well as with cell proliferation and migration activities. This study has provided crucial evidence on the importance of these natural antioxidant compounds on the wound healing properties of OPL.

Synthesis of 2,6-trans- and 3,3,6-trisubstituted tetrahydropyran-4-ones from Maitland-Japp derived 2H-dihydropyran-4-ones: a total synthesis of diospongin B.

6-Substituted-2H-dihydropyran-4-one products of the Maitland-Japp reaction have been converted into tetrahydropyrans containing uncommon substitution patterns. Treatment of 6-substituted-2H-dihydropyran-4-ones with carbon nucleophiles led to the formation of tetrahydropyran rings with the 2,6-trans-stereochemical arrangement. Reaction of the same 6-substituted-2H-dihydropyran-4-ones with l-Selectride led to the formation of 3,6-disubstituted tetrahydropyran rings, while trapping of the intermediate enolate with carbon electrophiles in turn led to the formation 3,3,6-trisubstituted tetrahydropyran rings. The relative stereochemical configuration of the new substituents was controlled by the stereoelectronic preference for pseudo-axial addition of the nucleophile and trapping of the enolate from the opposite face. Application of these methods led to a synthesis of the potent anti-osteoporotic diarylheptanoid natural product diospongin B.

A Maitland-Japp inspired synthesis of dihydropyran-4-ones and their stereoselective conversion to functionalised tetrahydropyran-4-ones.

The Maitland-Japp reaction has been extended to the synthesis of highly functionalised dihydropyran-4-ones. These dihydropyran-4-ones can in turn be converted stereoselectively into tetrahydropyran-4-ones with tertiary and quaternary stereocentres via the one-pot addition of hydride or carbon nucleophiles and trapping with carbon electrophiles. The utility of this method is demonstrated by providing access to the functionalised tetrahydropyran units present in a component of the Civet fragrance and the anticancer polyketide lasonolide A.

Strategies for the construction of tetrahydropyran rings in the synthesis of natural products.

This review focuses on the methodology used for the construction of tetrahydropyran (THP) rings in the synthesis of natural products over the last seven years. While methods like cyclisation onto oxocarbenium ions, reduction of cyclic hemi-ketals, Michael reactions, hetero-Diels-Alder cycloadditions and cyclisations onto epoxides continue to find application, several other strategies including metal-mediated cyclisations, ring-closing metathesis, radical cyclisations and carbocation cyclisations have also found use. This review is intended to provide an overview of the area for those who are unfamiliar, and to refresh and remind those who do work in the area of the exciting developments in the field.

Two new xanthones from Calophyllum nodusum (Guttiferae).

The air-dried powdered stem bark of Calophyllum nodusum (Guttiferea) collected from Sandakan (Sabah, Malaysia), was extracted sequentially with hexane, chloroform and methanol. The solvents were removed by rotary evaporator to give dark viscous extracts. Detailed and repeated chromatographic separation of the extracts lead to isolation of two new xanthones, identified as nodusuxanthone and trapezifolixanthone A. Other common terpenoids such as betulinic acid, lupeol, stigmasterol and friedelin were also isolated from the extracts and identified. The structures of the compounds were established by detailed spectral analysis and comparison with previously reported data.