One-pot reactions of 2,4-(dioxobutylidene)phosphoranes. Efficient synthesis of 4-(2-hydroxybenzoyl)salicylic acid derivatives and buta-1,3-diene-1,4-dicarboxylates

Domino reactions of chromones with activated carbonyl compounds

Domino reactions of chromones with activated carbonyl compounds, such as dimethyl acetone-1,3-dicarboxylate and 1,3-diphenylacetone, and with 1,3-bis(silyloxy)-1,3-butadienes, electroneutral equivalents of 1,3-dicarbonyl dianions, allow for a convenient synthesis of a great variety of products. The regioselectivity and course of the reaction depends of the substituent located at carbon C3 of the chromone moiety and also on the type of nucleophile employed.

Advances in chromone-based reactants in the ring opening and skeletal reconstruction reaction: access to skeletally diverse salicyloylbenzene/heterocycle derivatives

Salicyloylbenzene/heterocycles are privileged scaffolds found in many natural products and bioactive molecules. Numerous useful approaches for the preparation of these privileged scaffolds have been developed in recent years. Among these approaches, chromone-based reactants have demonstrated their importance in the synthesis of these salicyloylbenzene/heterocycle scaffolds with structural complexity and potential biological appeal. In this review, the recent advances in the synthesis of salicyloylbenzene/heterocycles are summarized and discussed according to the chromone-based reactants which could be achieved in one step via ring-opening and skeletal reconstruction reactions. Both the mechanisms and the applications of the corresponding products in organic and medicinal chemistry are also described.

Crystal structure and Hirshfeld surface analysis of 2-[(2-oxo-2H-chromen-4-yl)-oxy]acetic acid dimethyl sulfoxide monosolvate

The title compound, C11H8O5·(CH3)2SO, is a new coumarin derivative. The asymmetric unit contains two coumarin mol-ecules (A and B) and two di-methyl-sulfoxide solvent mol-ecules (A and B). The dihedral angle between the pyran and benzene rings in the chromene moiety is 3.56 (2)° for mol-ecule A and 1.83 (2)° for mol-ecule B. In mol-ecule A, the dimethyl sulfoxide sulfur atom is disordered over two positions with a refined occupancy ratio of 0.782 (5):0.218 (5). In the crystal, mol-ecules are linked by O-H⋯O hydrogen bonds, forming chains running along the c-axis direction. The chains are linked by C-H⋯O hydrogen bonds, forming layers parallel to the ac plane. In addition, there are also C-H⋯π and π-π inter-actions present within the layers. The inter-molecular contacts in the crystal have been analysed using Hirshfeld surface analysis and two-dimensional fingerprint plots, which indicate that the most important contributions to the packing are from H⋯H (33.9%) and O⋯H/H⋯O (41.2%) contacts.

The crystal structures of two new coumarin derivatives: 2-(4-{2-[(2-oxo-2H-chromen-4-yl)-oxy]acet-yl}piperazin-1-yl)acetamide and N-(2,4-di-meth-oxy-benz-yl)-2-[(2-oxo-2H-chromen-4-yl)-oxy]acetamide

The title compounds, 2-(4-{2-[(2-oxo-2H-chromen-4-yl)-oxy]acet-yl}piperazin-1-yl)acetamide, C17H19N3O5, (I), and N-(2,4-di-meth-oxy-benz-yl)-2-[(2-oxo-2H-chromen-4-yl)-oxy]acetamide, C20H19NO6, (II), are new coumarin derivatives. In compound (I), the six-membered piperazine adopts a chair conformation. The dihedral angles between the mean planes of the chromene ring and amide plane is 82.65 (7)° in (I) and 26.2 (4)° in (II). The dihedral angles between the mean planes of the chromene ring and the four planar C atoms of the piperazine ring in (I) and the benzene ring in (II) are 87.66 (6) and 65.0 (4)°, respectively. There are short intra-molecular contacts in both mol-ecules forming S(5) ring motifs, viz. N-H⋯N and C-H⋯O in (I), and N-H⋯O and C-H⋯N in (II). In the crystals of both compounds, mol-ecules are linked by N-H⋯O hydrogen bonds, forming chains along [10] in (I) and [010] in (II). The chains are linked by C-H⋯O hydrogen bonds, forming layers parallel to the ab plane in the crystals of both compounds. In the crystal of (I), there are also C-H⋯π and offset π-π inter-actions [inter-centroid distance = 3.691 (1) Å] present within the layers. In the crystal of (II), there are only weak offset π-π inter-actions [inter-centroid distance = 3.981 (6) Å] present within the layers. The inter-molecular contacts in the crystals of both compounds have been analysed using Hirshfeld surface analysis and two-dimensional fingerprint plots.

Selective syntheses of diversely substituted 2-hydroxy-4′-hydroxybenzophenones through [4 + 2] or [3 + 3] annulation of penta-3,4-dien-2-ones with 3-formylchromones

A selective synthesis of 2-hydroxy-4′-hydroxybenzophenones or their 3′-acylated counterparts via the cascade reactions of 3-formylchromones with diversely substituted penta-3,4-dien-2-ones is presented.

A comparison of the structures of some 2- and 3-substituted chromone derivatives: a structural study on the importance of the secondary carboxamide backbone for the inhibitory activity of MAO-B

The crystal structures of the 3-substituted tertiary chromone carboxamide derivative, C17H13NO3, N-methyl-4-oxo-N-phenyl-4H-chromene-3-carboxamide (1), and the chromone carbonyl pyrrolidine derivatives, C14H13NO3, 3-(pyrrolidine-1-carbon-yl)-4H-chromen-4-one (3) and 2-(pyrrolidine-1-carbon-yl)-4H-chromen-4-one (4) have been determined. Their structural features are discussed and compared with similar compounds namely with respect to their MAO-B inhibitory activities. The chromone carboxamide presents a -syn conformation with the aromatic rings twisted with respect to each other [the dihedral angle between the mean planes of the chromone system and the exocyclic phenyl ring is 58.48 (8)°]. The pyrrolidine derivatives also display a significant twist: the dihedral angles between the chromone system and the best plane formed by the pyrrolidine atoms are 48.9 (2) and 23.97 (12)° in (3) and (4), respectively. Compound (3) shows a short C-H⋯O intra-molecular contact forming an S(7) ring. The supra-molecular structures for each compound are defined by weak C-H⋯O hydrogen bonds, which link the mol-ecules into chains and sheets. The Cambridge Structural Database gave 45 hits for compounds with a pyrrolidinecarbonyl group. A simple statistical analysis of their geometric parameters is made in order to compare them with those of the mol-ecules determined in the present work.

Synthesis of 6-substituted salicylates via biomimetic aromatization utilizing the cross metathesis of a vinyl dioxinone with homoallylic alcohols

We herein report biomimetic syntheses of 6-substituted salicylates from the cross metathesis of 2,2-dimethyl-6-vinyl-1,3-dioxin-4-one with homoallylic alcohols, oxidation, and aromatization of the intermediate enone–dioxinones. Of particular note is the use of the catalyst 1,4-diazabicyclo[2.2.2]octane in the microwave thermolytic ketene generation and trapping, cyclization, and dehydration reaction sequence.

Salicylic acid derivatives: synthesis, features and usage as therapeutic tools

INTRODUCTION

In the field of medicinal chemistry, there is a growing interest in the use of small molecules. Although acetyl salicylic acid is well known for medical applications, little is known about other salicylic acid derivatives, and there is serious lack of data and information on the effects and biological evaluation that connect them.

AREAS COVERED

This review covers the synthesis and drug potencies of salicylic acid derivatives. After a brief overview of the information on salicylic acid and its features, a detailed review of salicylic acids as drugs and prodrugs, usage as cyclooxygenase inhibitors, properties in plants, synthesis and recent patents, is developed.

EXPERT OPINION

Salicylic acid research is still an important area and innovations continue to arise, which offer hope for new therapeutics in related fields. It is anticipated that this review will guide the direction of long-term drug/nutraceutical safety trials and stimulate ideas for future research.

Curcuminoid biosynthesis by two type III polyketide synthases in the herb Curcuma longa

Curcuminoids found in the rhizome of turmeric, Curcuma longa, possess various biological activities. Despite much attention regarding the biosynthesis of curcuminoids because of their pharmaceutically important properties and biosynthetically intriguing structures, no enzyme systems have been elucidated. Here we propose a pathway for curcuminoid biosynthesis in the herb C. longa, which includes two novel type III polyketide synthases. One of the type III polyketide synthases, named diketide-CoA synthase (DCS), catalyzed the formation of feruloyldiketide-CoA by condensing feruloyl-CoA and malonyl-CoA. The other, named curcumin synthase (CURS), catalyzed the in vitro formation of curcuminoids from cinnamoyldiketide-N-acetylcysteamine (a mimic of the CoA ester) and feruloyl-CoA. Co-incubation of DCS and CURS in the presence of feruloyl-CoA and malonyl-CoA yielded curcumin at high efficiency, although CURS itself possessed low activity for the synthesis of curcumin from feruloyl-CoA and malonyl-CoA. These findings thus revealed the curcumin biosynthetic route in turmeric, in which DCS synthesizes feruloyldiketide-CoA, and CURS then converts the diketide-CoA esters into a curcuminoid scaffold.