Seven undescribed diterpenoids paraflexinols A–G (1–7), possessing a fifteen-membered macrocyclic ring, have been isolated from the ethyl acetate extract of the soft coral Paralemnalia thyrosides. The structures of 1–7 have been established by the detailed spectroscopic analysis, including 2D NMR spectroscopy, while their absolute configurations were determined using a modified Mosher's method for 1–3, 6, and 7. For over four decades after the first discovery of the ancestor of these compounds flexibilene (8) from the soft coral Sinularia flexibilis until the current report, no flexibilane-based diterpenoids had been isolated or identified. This study provides detailed NMR data for metabolites of this type for the first time.

A novel, simple and efficient CuBr2-catalyzed reaction of 3,6-dihydroxyphthalonitrile with arylamines to produce 1,3-bis(arylimino)isoindolines has been developed. Under the optimal conditions, thirteen 1,3-bis-(arylimino)isoindoline derivatives and one 2,3-bis(1H-benzo [d]- imidazole-2-yl)benzene-1,4-diol were obtained in yields among 51–93%. A reasonable mech-anism involving promotion of CuBr2 to 3,6-dihydroxyphthalonitrile is proposed based on experimental results. The optical properties of some products were determined, which resulted in a potential proton transferring dye, 3e (1,3-bis(2-methoxyphenylimino)-isoindoline-4,7-diol), and a pH fluorescent probe in pH range of 7.00–9.30, 3f (1,3-bis(4-hydroxyphenylimino)-isoindoline-4,7-diol).

A novel and efficient palladium-catalyzed direct mono and tetraarylation of tetrathienylethene with various arylbromides to synthesize donor-acceptor system of tetrathienylethene-arene (TTE-Ar) luminophores is reported. The mono- and tetra-arylated TTEs shown an emissive phenomenon, including photoluminescence in various organic solvents and aggregation induced emission (AIE) effect because TTE acts both as an electron-donor for intramolecular charge transfer (ICT) and as activator for AIE. The photoluminescence and AIE of these aryl-substituted TTEs are characterized.

Several heterocyclic molecular frameworks have been regarded as privileged structure in the field of medicinal chemistry. These privileged structure or scaffolds or moieties display wide range of biological activities. Therefore, synthesis of the heterocycles having these privileged structures is an essential part in the drug discovery and development process. In this study, an attempt has been made to review and summarize recent developments in the synthetic strategies of 1,5-benzothiazepine and their derivatives. Various recent synthetic strategies including general, one-pot, green, ionic liquid, enantioselective synthesis and asymmetric hydrogenation of the 1,5-benzothiazepine are reviewed and summarized. To the best of our knowledge, the present manuscript is the complete compilation on the recent developments in the synthetic strategies of the 1,5-benzothiazepines.

Abstract not available

A mild, greener approach via tandem-Michael-cyclization cascade reaction towards the construction of a group of di- and tri-differently substituted indolizine with a broad scope of the substrate is described. The synthetic route to indolizine having different substituents, benzoyl at C5, alkyl/aryl, at C6, and ester at C7 positions is established where different N-alkylated pyrrole-2-carbaldehydes and electron-deficient acetylenes are employed for the synthesis of pyridine moiety. This methodology features water-mediated reactions compatible with various functional groups affording indolizines in good yield without using any oxidant, additive, or catalyst as well. Successfully this methodology has been extended to prepare dicarboxylate and nitrile-substituted indolizines which can be proven important from a biological activity point of view in future.

Design of excellent circularly polarized luminescence (CPL) emitters requires chiral molecules with large transition magnetic dipole moments (TMDM, |m|). In this work [5]-, [7]-, and [9]helicene derivatives with 2,1,3-thiadiazole rings at both ends, TD[5]H, TD[7]H, and TD[9]H, were designed and synthesized. We revealed that TD[9]H showed an excellent CPL with a large glum of +0.04 at 520 nm in toluene, which was significantly larger than that of unsubstituted carbo[7]helicene (glum = +0.008). Density functional theory (DFT) calculations suggested that the remarkable glum of TD[9]H was attributed to the magnetically allowed transition with a large TMDM (|m| = 2.3 × 10−20 erg G−1) for the S1→S0 transition.

A divergent synthesis to rare L-altro sugars and C-6 derivatives from easily available d-galactose is described. The important intermediate, L-altro epoxide 28, was provided by regioselective protections, regioselective 6-O-benzoylation/5-O-mesylation, and intramolecular SN2 inversion at C-5 as key steps. The following nucleophilic addition on the epoxide ring with H−, CN−, and N3− afforded the corresponding 6-deoxy-, 6-cyano-, and 6-azido-L-altrofuranosides, respectively. Hydrolysis of the epoxide 28 under acidic conditions furnished the 1,6-anhydro-L-altro sugar 38, which could undergo sequential thioglycosylation and oxidation to yield l-altrose-derived thioglycoside 40.

In this paper we describe the efficient synthesis of d-ribo-phytosphingosine and its analogues commencing from the easily available l-erythrose chiron, which already contained the future C-3 and C-4 stereocentres of our target compounds. Construction of the remaining C-2 stereochemistry relied on aza-Claisen rearrangements to establish the desired vicinal aminoalcohol motif. The aliphatic chain was introduced by means of an olefin cross metathesis process. Completion of this phytosphingolipid synthesis was then achieved through the suitable selection of functional group interconversions, accompanied by selective deprotection protocols. Preliminary in vitro experiments revealed higher antiproliferative activity of the unnatural d-arabino-phytosphingosine 3. HCl in comparison to cisplatin against three of the five cancer cell lines evaluated, with IC50 values ranging from 4.17 μM to 7.63 μM. Moreover, compound 3. HCl has better inhibitory effects on the proliferation of the aforementioned malignant cell lines than its natural stereochemical congener 2. HCl.

A cobalt-catalyzed C–H activation and isocyanide insertion of tryptamine derivatives has been developed for the construction of indole-2-carboxamide scaffolds. By using Co(OAc)2·4H2O as the non-noble catalyst, the reaction worked well to give various indole-2-carboxamides in moderate to high yields. Furthermore, the mechanistic experiments indicated that the Co(III) species was the active catalyst in a non-radical reaction pathway. Notably, silver salt as the oxidant could be recycled and reused.

The reaction between aryl diazonium salts and aryl sulphonyl hydrazones in ethanol-pyridine is a simple, metal-free route to the synthesis of 2,5-diaryltetrazoles. However, it is difficult to use for polyaromatic precursors that are poorly soluble in such a polar medium. We show here that the choice of another reaction solvent such as acetone-pyridine can, in many cases, lead to perfect control of the reaction and to the spontaneous precipitation of the targeted tetrazoles.

Cu(II) salt has been found to be an efficient catalyst for the regioselective synthesis of a series of novel indolizino [8,7-b]indole derivatives with pyrimidine tethers via three-component annulation of 1-formyl-9H-β-carbolines (Kumujian C), 2-amino-pyrimidines and terminal alkynes. The reactions proceeds through Cu-catalysed A3-coupling followed by intramolecular cyclisation in a cascade manner. The scope of strategy has been exemplified with a library of biologically interesting 25 indolizino [8,7-b]indoles with pyrimidine tethers which mimics several natural products.

K2S2O8 promoted dehydrative trifluoromethylated reaction between allylic alcohols and Langlois reagent were described air atmosphere in high yields. A tentative radical mechanism is proposed.

Nitrogen-containing macrocycles have attracted sustained attention because of their fascinating structures and extensive applications in organic chemistry, therapeutic developments, and materials science. The nitrogen atoms in the macrocycles play important roles in the interaction with metal cations or small molecules, endowing their potential in catalysis, fluorescent sensors, and host–guest chemistry. In this context, herein we summarize highly symmetric nitrogen-containing N3/N4/N6 macrocycles comprising pyrroles, pyridines, quinolines, and (iso)indoles as key N-heteroarenes. The direct and indirect connectivity of N-heteroarene subunits allows for the construction of both flat and non-flat cyclic architectures. The synthesis, structure, and properties of these macrocycles are highlighted.

Alkoxymagnesium halide is demonstrated as an effective catalyst for the carbonyl hydroboration of esters, aldehydes, and ketones. This study reports the smooth hydroboration of a variety of esters, aldehydes, and ketones with ethoxymagnesium chloride (EtOMgCl) and pinacolborane under mild reaction conditions (low catalyst loading 0.3 mol% for aldehydes and ketones, 5 mol% for esters, room temperature). Among the tested alkoxymagnesium chlorides, EtOMgCl was the optimum catalyst in terms of yield and selectivity for esters. Moreover, the designed protocol afforded the chemoselective hydroboration of esters in good yields with high selectivity.

An efficient and facile one-pot, multi-component reaction for the regio- and diastereoselective synthesis of novel dispirocyclopentanebisoxindoles has been reported by a reaction between phenyl-2-(triphenylphosphoranylidene)ethanone and isatin derivatives. The great advantages of this synthetic protocol are the minimal reaction steps, short reaction time, and operational simplicity. In consequence, a variety of new dispirocyclopentanebisoxindole derivatives with potential medicinal applications were synthesized through one-pot and multi-component reaction in high to excellent yields.

The total synthesis of tanzawaic acid A, a potent antifungal active against Rhizopus oryzae, has been achieved. Key features of the synthetic strategy include the Heck reaction between a sterically hindered triflate and methyl acrylate and Evans alkylation/Friedel–Crafts acylation/stereoselective hydrogenation for the stereoselective construction of the triflate with a tetrahydronaphthalene unit. The practical total synthesis provided tanzawaic acid A with an overall yield of 29% over 20 steps.

Abstract not available

Cross-dimerization reactions that employ nonequivalent 9-fluorenones have been accomplished. This cross-dimerization doesn't employ any additives such as metals and salts, that was unthinkable heretofore. Because the cross-couplings were achieved by phosphite solvent alone, they were not only operationally simple but also productively efficient owing to suppression of homo-dimerization. Significantly, the resulting single spiroketones were transformed into a hexacycle core of dibenzo[g,p]chrysene having twofold tert-butyl groups and twofold halogen atoms. The synthesis of solution-processable and multi-tunable hexacycle, coupled with the mechanistic aspects, enables general access to non-planar polyarenes from the viewpoint of diversity-oriented synthesis.

Synthesis of four derivatives of chiral bis-thiourea have been prepared from (S)-(1- isocyanatoethyl)benzene and diamines. The bis-thiourea derivatives were scanned as Chiral Solvating Agents (CSA) for detecting discrimination of optically pure acids by 1H NMR spectroscopy. Addition of amine during NMR experiments was found essential to effect deprotonation of carboxylic acid substrates. The present CSA were found to show effective chiral discrimination of neutral analytes such as tetrahydropyrimidine derivatives. Further they showed good molecular recognition in case of 1,4-dihydropyridine carboxylic acid, an intermediate of cardiovascular drug Benidipine-HCl and ibuprofen.