Total Synthesis of Tovophyllin B

Solvent-free synthesis of 1-amidoalkyl-2-naphthol and 3-amino-1-phenyl-1H benzo[f]chromene-2-carbonitrile derivatives by Fe3O4@enamine-B(OSO3H)2 as an efficient and novel heterogeneous magnetic nanostructure catalyst

A green procedure for the one-pot three-component synthesis of 1-amidoalkyl-2-naphthol and 3-amino-1-phenyl-1H benzo[f]chromene-2-carbonitrile derivatives from the reaction of 2-naphtol, aldehydes, and malononitrile/acetamide in the presence of a catalytic amount of Fe3O4@enamine-B(OSO3H)2 as an efficient and novel heterogeneous magnetic nanostructure catalyst is described. The catalyst was characterized using Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), vibrating sample magnetometry (VSM), energy dispersive X-ray spectroscopy (EDX), and X-ray diffraction (XRD). These strategies possess some merits such as simple work-up method, easy preparation of the catalyst, short reaction times, good-to-high yields, and non-use of hazardous solvents during all steps of the reactions. Moreover, due to the magnetic nature of the catalyst, it was readily recovered by magnetic decantation and can be recycled at least six runs with no considerable decrease in catalytic activity.

Yicathins B and C and Analogues: Total Synthesis, Lipophilicity and Biological Activities

Natural products have always been an important source of new hits and leads in drug discovery, with the marine environment being regarded as a significant source of novel and exquisite bioactive compounds. Yicathins B and C are two marine-derived xanthones that have shown antibacterial and antifungal activity. Herein, the total synthesis of these yicathins and six novel analogues is reported for the first time. As marine natural products tend to have very lipophilic scaffolds, the lipophilicity of yicathins and their analogues was evaluated in the classical octanol/water system and a biomimetic model-based system. As the xanthonic nucleus is a "privileged structure", other biological activities were evaluated, namely antitumor and anti-inflammatory activities. An interesting anti-inflammatory activity was identified for yicathin analogues that paves the way for the design of dual activity (anti-infective and anti-inflammatory) marine-inspired xanthone derivatives.

Synthesis of Novel 15-aryl-2,3,4,15-tetrahydrochromeno[2′,3′:4,5] Pyrimido[6,1-b]Quinazoline-1,9-diones

A new series of 15-aryl-2,3,4,15-tetrahydrochromeno[2′,3′:4,5]pyrimido[6,1-b]quinazoline-1,9-diones was synthesised by the cyclisation of methyl anthranilate with ethyl N-(3-cyano-5-oxo-4-aryl-5,6,7,8-tetrahydro-4H-chromen-2-yl)formimidate derivatives, which were obtained by the reactions of 2-amino-5-oxo-4-aryl-5,6,7,8-tetrahydro-4H-chromene-3-carbonitrile derivatives and triethyl orthoformate. The structure of the 2,4-dichlorophenyl derivative was further determined by single crystal X-ray diffraction analysis.

One-pot synthesis of various 2-amino-4H-chromene derivatives using a highly active supported ionic liquid catalyst

Supported ionic liquid phase catalyst was synthesized and applied for the synthesis of chromene derivatives under solvent-free conditions.

Synthesis of Novel 2-Methyl and 2-Cyanomethyl-12-Aryl-8,12-Dihydro-9H-cHromeno[3,2-e][1,2,4]Triazolo[1,5-c]Pyrimidin-11(10H)-One Derivatives

2-Methyl and 2-cyanomethyl-12-aryl-8,12-dihydro-9H-chromeno[3,2-e][1,2,4]triazolo[1,5-c]pyrimidin-11(10H)-one derivatives were synthesised by the cyclisations of acetic anhydride or ethyl cyanoacetate with chromeno[2,3-d]pyrimidine derivatives, which were obtained by the reactions of hydrazine monohydrate and formimidate derivatives. In addition, 2,9,9-trimethyl-12-(p-tolyl)-8,12-dihydro-9H-chromeno[3,2-e][1,2,4]triazolo[1,5-c]pyrimidin-11(10H)-one and 2-cyanomethyl-12-phenyl-8,12-dihydro-9H-chromeno[3,2-e][1,2,4]triazolo[1,5-c]pyrimidin-11(10H)-one were further determined by single-crystal X-ray diffraction analysis.

“On water” synthesis of highly functionalized 4H-chromenes via carbon–carbon bond formation under microwave irradiation and their antibacterial properties

Microwave assisted synthesis catalyst-free synthesis water as a solvent anti bacterial properties.

Synthesis of functional 4H-chromenes from phenols and acetophenones under solvent- and metal-free conditions

Sulfuric-acid-promoted tandem reaction of phenols with acetophenones under solvent- and metal-free conditions has been developed, which afforded functional 4H-chromenes in good yields with water as the side product.

Total Syntheses of Proposed (±)-Trichodermatides B and C

Total syntheses of putative (±)-trichodermatides B and C are described. These efficient syntheses feature the oxa-[3 + 3] annulation strategy, leading to B and C along with their respective C2-epimers. However, these synthetic samples are spectroscopically very different from the natural products. DFT calculations of C13 chemical shifts are conducted and the predicted values are in good agreement with those of synthetic samples, thereby questioning in the accuracy of structural assignments of trichodermatides B and C.

Ethyl 2-amino-4-(4-methyl-1,3-thia-zol-5-yl)-5-oxo-4H,5H-pyrano[3,2-c]chromene-3-carboxyl-ate

There are two independent mol-ecules in the asymmetric unit of the title compound, C19H16N2O5S, in which the thia-zole rings make dihedral angles of 80.89 (11) and 84.81 (11)° with the pyrano[3,2-c]chromene ring systems. An intra-molecular N-H⋯O hydrogen bond involving the amino group occurs in each independent mol-ecule. In the crystal, the amino groups are involved in N-H⋯O and N-H⋯N hydrogen bonds.

Ethyl 2-amino-4-(4-fluoro-phen-yl)-6-meth-oxy-4H-benzo[h]chromene-3-carboxyl-ate

In the title compound, C₂₃H₂₀FNO₄, the fluoro-substituted benzene ring is approximately perpendicular to the mean plane of the 4H-benzo[h]chromene ring system [maximum deviation = 0.264 (1) Å], with a dihedral angle of 83.79 (6)°. The pyran ring adopts a flattened boat conformation. The meth­oxy group is slightly twisted from the attached benzene ring of the 4H-benzo[h]chromene moiety [C—O—C—C = −2.1 (2)°]. An intra­molecular N—H⋯O hydrogen bond generates an S(6) ring motif. In the crystal, mol­ecules are linked by N—H⋯O and N—H⋯F hydrogen bonds into a layer parallel to the bc plane. The crystal packing also features C—H⋯π inter­actions.

Total syntheses of graphisin A and sydowinin B

Efficient syntheses of the highly substituted benzophenone graphisin A and the xanthone sydowinin B are described. Key steps involve aryl anion addition to substituted benzaldehyde derivatives, subsequent methyl ester installation, and dehydrative cyclization. Oxidation of graphisin A led to a spirodienone derived from a highly substituted benzoquinone intermediate.

Constructing the Architecturally Distinctive ABD-Tricycle of Phomactin A through an Intramolecular Oxa-[3 + 3] Annulation Strategy

Our efforts in constructing the ABD-ring of phomactin A through an intramolecular oxa-[3 + 3] annulation strategy is described. This struggle entailed finding a practical and efficient preparation of annulation precursor, and a realization of the unexpected competing regioisomeric pathway. The success entailed accessing the A-ring through Diels-Alder cycloaddition of Rawal's diene. Furthermore, the discovery that the regioisomers from the annulation existed as atropisomers with respect to the D-ring olefin and that they could be equilibrated to the desired ABD-tricycle, allowing large quantities of tricycle to be accessed.

Total synthesis of (±)-phomactin A. Lessons learned from respecting a challenging structural topology

Our struggles and ultimate success in achieving a total synthesis of phomactin A are described. Our strategy features an intramolecular oxa-[3 + 3] annulation to construct its unique ABD-tricyclic manifold. Although the synthesis would constitute a distinctly new approach with the 12-membered D-ring of phomactin A being assembled simultaneously with the 1-oxadecalin at an early stage, the ABD-tricycle represents a unique structural topology that would pose a number of unprecedented challenges. One challenge concerned elaborating this tricycle to have oxygenation at the proper carbon atoms. To overcome this, we would utilize a Kornblum-DeLaMare ring-opening of a peroxide bridge as well as a challenging late-stage 1,3-allylic alcohol transposition. Further, the structural intricacies of the ABD-tricycle were uncovered by a conformational analysis that would be critical for the C5a-homologation.

Synthesis of 4H-chromene, coumarin, 12H-chromeno[2,3-d]pyrimidine derivatives and some of their antimicrobial and cytotoxicity activities

Condensation of 3-N,N-diethylaminophenol (1) with α-cyanocinnamonitriles (2a-c) and ethyl α-cyanocinnamates (2d-f) provided compounds 3a-f and 4a-c. 12H-Chromeno[2,3-d]pyrimidine derivatives 6, 11-13 and 16 were obtained by treatment of 4H-chromene compounds (3) with different electrophiles followed by nucleophilic reagents. Structures of these compounds were established on the basis of IR, UV, 1H NMR, 13C NMR and MS data. Some of the new compounds were evaluated for antimicrobial and cytotoxicity activities.