Titanocene(III) chloride mediated radical-induced synthesis of 3,4-dihydroisocoumarins: synthesis of (±)-hydrangenol, (±)-phyllodulcin, (±)-macrophyllol and (±)-thunberginol G

A review on natural sweeteners, sweet taste modulators and bitter masking compounds: structure-activity strategies for the discovery of novel taste molecules

Growing demand for the tasty and healthy food has driven the development of low-calorie sweeteners, sweet taste modulators, and bitter masking compounds originated from natural sources. With the discovery of human taste receptors, increasing numbers of sweet taste modulators have been identified through human taste response and molecular docking techniques. However, the discovery of novel taste-active molecules in nature can be accelerated by using advanced spectrometry technologies based on structure-activity relationships (SARs). SARs explain why structurally similar compounds can elicit similar taste qualities. Given the characterization of structural information from reported data, strategies employing SAR techniques to find structurally similar compounds become an innovative approach to expand knowledge of sweeteners. This review aims to summarize the structural patterns of known natural non-nutritive sweeteners, sweet taste enhancers, and bitter masking compounds. Innovative SAR-based approaches to explore sweetener derivatives are also discussed. Most sweet-tasting flavonoids belong to either the flavanonols or the dihydrochalcones and known bitter masking molecules are flavanones. Based on SAR findings that structural similarities are related to the sensory properties, innovative methodologies described in this paper can be applied to screen and discover the derivatives of taste-active compounds or potential taste modulators.

Addition of Benzyl Halides to Aldehydes and Imines Using Photoactivated TDAE: Access to 3,4-Dihydroisocoumarins, 1,2-Diarylethanols, and 1,2-Diarylcarbamates under Metal-Free Conditions

We describe herein the intermolecular addition reaction of benzyl halides to aldehydes and imines using photoactivated tetrakis(dimethylamino)ethylene (TDAE) as superphotoreductant. 3,4-Dihydroisocoumarins, 1,2-diarylethanols, and 1,2-diarylcarbamates were obtained with good functional group tolerance using simple, mild, and metal-free conditions.

Valuable building block for the synthesis of lunularic acid, hydrangeic acid and their analogues

A new functionalised sulphone-based building block has been synthesised that enabled C-C bond formation through Julia olefination. The utility of developed building block was demonstrated by successful synthesis of two natural products lunularic acid, hydrangeic acid and initial libraries of their analogues.

Convenient Syntheses of 3-Aryl-3,4-Dihydroisocoumarins

A convenient method for the synthesis of naturally occurring 3,4-dihydroisocoumarins by judicious use of Friedel-Craft acylation, regioselective formylation and oxidative cyclisation reactions is described. O-methylated analogues of montroumarin and thunberginols C and D and have been synthesised using 3,5-dimethoxyphenylacetic acid as a starting material. Furthermore, the starting material 3,5-dimethoxyphenylacetic acid was synthesised by a route involving an oxidative Nef reaction.

Antioxidant and free radical-scavenging activity of constituents from two Scorzonera species

The aim of this study was to investigate the secondary metabolites content of Scorzonera papposa DC., an edible plant eaten in the desert region of Jordan and to assess its antioxidant and free radical-scavenging activity. By using this bioassay-oriented approach nine compounds, including the new natural compounds (6-trans-p-coumaroyl)-3-O-β-D-glucopyranosyl-2-deoxy-D-riburonic acid (1), (6-cis-p-coumaroyl)-3-O-β-D-glucopyranosyl-2-deoxy-D-riburonic acid (2a), (6-trans-p-coumaroyl)-3-O-β-D-glucopyranosyl-2-deoxy-D-riburonic acid methyl ester (3), and (6-trans-p-coumaroyl)-3-O-β-D-glucopyranosyl-(5-acetyl)-2-deoxy-D-riburonic acid (4), having the rare deoxy-D-riburonic acid moiety, were isolated. Their structures were elucidated by UV, MS, (1)H and (13)C NMR and 2D NMR. The antioxidant activity of the S. papposa pure compounds and of related derivatives isolated from another Scorzonera species (S. judaica Eig.) was also tested. The Relative Antioxidant Capacity Index (RACI) was applied as an integrated method to compare the antioxidant activities obtained using different chemical methods.

Recent applications of Cp2TiCl in natural product synthesis

Titanocene(iii)-based approaches have been demonstrated to be useful in the straightforward syntheses of many natural products from readily available starting materials.

Medicinal flowers. XXXX . Structures of dihydroisocoumarin glycosides and inhibitory effects on aldose reducatase from the flowers of Hydrangea macrophylla var.thunbergii

Six dihydroisocoumarin glycosides, florahydrosides I and II, thunberginol G 8-O-β-d-glucopyranoside, thunberginol C 8-O-β-d-glucopyranoside, 4-hydroxythunberginol G 3'-O-β-d-glucopyranoside, and thunberginol D 3'-O-β-d-glucopyranoside, have been isolated from the flowers of Hydrangea macrophylla Seringe var. thunbergii Makino (Saxifragaceae) together with 20 known compounds. The chemical structures of the new compounds were elucidated on the basis of chemical and physicochemical evidence. Among the constituents, acylated quinic acid analog, neochlorogenic acid, was shown to substantially inhibit aldose reductase [IC50=5.6 µm]. In addition, the inhibitory effects on aldose reductase of several caffeoylquinic acid analogs were examined for structure-activity relationship study. As the results, 4,5-O-trans-p-dicaffeoyl-d-quinic acid was found to exhibit a potent inhibitory effect [IC50=0.29 µm].

The psymberin story--biological properties and approaches towards total and analogue syntheses

Psymberin is a marine natural product which has attracted a great deal of interest since its isolation: While the highly cytotoxic compound was detected early on as an ingredient in a marine sponge, it took over a decade and 600 additional samples for the structure to eventually be assigned. In the last eight years fascinating synthetic and biosynthetic investigations have led to a more detailed understanding as well as a new starting point for structure-activity studies towards new antitumor compounds. The Review gives an in-depth insight into the progress in the field of the marine polyketide psymberin and demonstrates how organic synthesis is influencing neighboring scientific subjects.

Synthesis and antibacterial evaluation of typharin analog: 6,8-dihydroxy-7-methyl-3-styryl-3,4-dihydroisocoumarin

Synthesis of the 6-hydroxy-7-methyl analog of typharin (8-dihydroxy-3-styryl-3,4-dihydroisocoumarin) isolated from the rhizomes of Typha capensis has been described. Direct condensation of 3,5-dimethoxy-4-methylhomophthalic acid (1) with cinnamoyl chloride at elevated temperature under inert conditions afforded 6,8-dihydroxy-7-methyl-3-styrylisocoumarin (2). Hydrolysis of isocoumarin to keto acid (3) followed by reduction and cyclodehydration of hydroxy acid analog (4) afforded ( ± )-6,8-dimethoxy-3-(4-methoxyphenyl)-3,4-dihydroisocoumarin (5). Demethylation of the latter using anhydrous aluminum chloride/ethane thiol furnished the title isocoumarin (6). Compounds (1-6) were screened for in vitro antibacterial activity against a representative panel of Gram-positive and Gram-negative bacteria using levofloxacin as the reference drug.

Synthesis, spectroscopic and structural study of trans- and cis-(±)-3-phenyl-4-(pyrrolidine-1-carbonyl)-isochroman-1-ones

Synthesis, spectroscopic and structural study of trans- and cis-(±)-3-phenyl-4-(pyrrolidine-1-carbonyl)-isochroman-1-ones is performed in order to obtain the correlation between the crystal structure and spectroscopic properties of both isomers in solid-state. The methods such as single crystal X-ray diffraction, conventional and linear-polarized IR-spectroscopy, UV-spectroscopy, mass spectrometry, ¹H and ¹³C NMR are employed. Quantum chemical ab initio and DFT calculations are performed, to support the experimental data for the electronic structure and optical properties.