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We describe the efficient total syntheses of naturally occurring tripeptides acidiphilamides A–C and epi-acidiphilamides A–C, which were prepared from commercially available l-phenyl alanine using hexafluorophosphate azabenzotriazole tetramethyl uronium (HATU) as peptide coupling reagent. The structures of the natural acidiphilamides A, B and C were characterized by NMR, MS and SOR data, which match those of natural products, whereas the structures of epi-acidiphilamides A, B and C were confirmed by 2D NMR studies.

An efficient and simple synthesis of various 3-(trifluoromethyl)chromones from enamino ketones is described. The key step in the synthesis involves the introduction of a trifluoromethyl (CF3) moiety onto a chromone structure. The significant features of this method include simple operational procedures, the high purity and yield of the product, and excellent regioselectivity.

An efficient and novel method for the preparation of unnatural α-amino acids (UAAs) containing 7-hydroxy-2,2-dimethyl-chroman via a 1,3-di-polar-cyloaddition reaction has been described. Using this method, various new ethyl 2-amino-3-(3-(7-hydroxy-2,2-dimethylchroman-6-yl)isoxazol-5-yl)propanoate derivatives have been prepared where the isoxazole ring is acting as a linker between alanine and chroman moieties. This is the first example of isoxazole-tethered 2,2-dimethylchroman-amino acid hybrids.

A new regioselective method for the synthesis of 2-aryl-5-benzoylpyridine derivatives has been developed. The reaction proceeds via ring opening and closing cascade mechanism (ROCC) of isoxazole to synthesize various functionalized pyridine derivatives. This is the first report for the preparation of 2,5-di-substituted pyridines using Fe/NH4Cl as a reducing reagent. Keywords: Isoxazole, 2,5-Disubstituted pyridines, ROCC mechanism, Fe/NH4Cl

An efficient synthesis of various 3-fluorochromones (3-fluoro-4H-chromene-4-ones) from enamino ketones by using Selectfluor is described. The key step in the synthesis involves tandem fluorination and cyclization to form 3-fluorochromones in good yields. The significant features of this method include simple operational procedures, a high purity of the product, and excellent regioselectivity.

Ag nanoparticles (AgNPs) catalyst material is bio-synthesized and fully examined using various spectroscopy and microscopy techniques. Further this synthesized material is used for hydroxylation reaction, for this purpose we developed a simple and versatile bio-based method from aryl boronic acids to phenol. The reaction was studied in the presence of low cost ligand in a hydrated reaction medium without any hazardous organic solvents, as a result a finite amount of yield was achieved in short time (

“A series of novel spirobiisoxazoline dibenzoquinone derivatives were synthesized starting from 2,5-dimethoxybenzaldehyde in a six-step synthetic sequence”. The key step [3 + 2] double 1,3-dipolar cycloaddition of oxime chloride with allenoate was performed under mild reaction conditions using sodium carbonate at ambient temperature. This is the first innovative synthesis of Spirobiisoxazoline Dibenzoquinone system where quinone ring is alkylated to isoxazoline moiety.

A series of novel 1, 2, 4-triazolo isoquinoline derivatives (8a-8p) were synthesized starting from 2-phenylethan-1-ol derivative (1) in a 7 step synthetic sequence. The key step in the scheme involves 1, 3-dipolar [3 + 2] cycloaddition of azomethine imine and ethyl cyanoformate as unknown reaction protocol. We have demonstrated the hydrolysis of both ester and benzoyl group in a single step and the corresponding carboxylic acid derivatives were coupled with various amines to generate unknown 1, 2, 4-triazolo isoquinoline derivatives The structures of the compounds (8a-8p) were characterized by 1H NMR, 13C NMR and HRMS analysis.

A new regioselective method for the synthesis of 3-(methylthio)-4H-chromen-4-one and 3-(phenylthio)-4H-chromen-4-one derivatives has been developed. The reaction between o-hydroxy-phenyl-functionalized enaminones and methylsulfinyl derivatives using T3P® gave good yields of chromone thioether derivatives. The reaction proceeds via domino chromone ring construction and C(sp2)–H bond sulfenylation under transition-metal-free conditions.

The synthesis of N-formamides from aromatic amines and formic acid using propylphosphonic anhydride (T3P®) as a green coupling reagent is described. By using this method, aryl, heteroaryl and fluorinated aryl-containing formamides were synthesized in high yield and purity. The significant features of this method include easy work up, high purity and reduced toxicity of the reaction.

An efficient synthesis of 4H-chromene-4-ones via enamino ketones, with cyclization by using T3P® under microwave heating is described. This is the first report for the synthesis of chromones by using T3P®. Significant features of this method include short reaction times and high-purity products.

An efficient method for the preparation of chromone based $$\upalpha $$ -amino acid derivatives by alkylation of glycinate schiff base with 3-bromomethyl chromone as well as 2-bromomethyl chromone has been described. Using this method, 2-amino-3-(4-oxo-2-chromenyl)propanoic acid and 2-amino-3-(4-oxo-3-chromenyl)propanoic acid, two novel chromone-amino acid conjugates have been prepared. Furthermore, the separation of chromone amino acid enantiomers by chiral column chromatography was accomplished. Synopsis: An efficient method for the preparation of chromone based $$\upalpha $$ -amino acid derivatives by alkylation of glycinate schiff base with 3-bromomethyl chromone as well as 2-bromomethyl chromone has been described. These conjugates can be considered as analogues of phenyl alanine where phenyl group has been replaced by chromone moiety.

The reaction of 1,3,4-oxathiazol-2-one derivative with 2-arylidene-1,3-indandione to furnish novel spiroindene-1,3-dione isothiazoline derivatives by Michael/1,3-dipolar [3+2]-cycloaddition reaction was investigated. The key 1,3-dipolar cycloaddition reaction step was examined in toluene solvent at reflux temperature to obtain mixture of two regioisomers (6a and 6b – 14a and 14b) and single isomers (15–20). The scope of this new reaction was demonstrated with many examples with high reactivity and yields.

A facile and versatile procedure for the synthesis of functionalized novel 2,5-diphenyl-5H-chromeno[4,3-d]pyrimidin-5-ol and (2,4-diphenylpyrimidin-5-yl) (2-hydroxyphenyl) methanone has been described. The key step in the synthesis involves the ANRORC reaction of 3-benzoyl chromones with benzamidines.

A novel and unexpected aryne insertion cascade reaction on 2-arylidene-1,3-indandiones via conjugate addition of fluoride followed by formal C–C insertion is developed to afford dibenzo[a,d]cycloheptanoid derivatives in good yields with a single isomer. This reaction represents a rare instance of cyclic enone C–C bond insertion (acyl-alkenylation) in aryne chemistry. Interestingly, 2-arylidene-1,3-indandiones bearing electron rich functional groups provided dibenz[a,c]anthracene-9,14-dione derivatives via [4 + 2] cycloaddition followed by ring expansion.

A simple and efficient synthesis has been developed for 1,2,4-traizole derivatives from 2-arylidene-1,3-indandiones and 1-methylhydrazine-1-carbonitrile in two steps with good yields. The reactions include formal [3 + 2] cycloaddition and skeletal rearrangement to provide amino hydrazones followed by T3P mediated dehydrogenative coupling. This method provides a new and useful strategy for synthesis of novel 1,2,4-triazole derivatives.

A series of novel diaziridinyl quinone thiadiazole hybrids (9a–9j) were synthesized starting from 2-hydroxy-5-methoxybenzoic acid 1 in a 7 step synthetic sequence. The key step in the scheme involves the nitrile sulfide cycloaddition reaction of oxathiazolone 4 with p-tosylcyanide to obtain 1,2,4-thiadiazole derivative 5. We have demonstrated that p-tosyl group of thiadiazole 5 can be displaced with various nitrogen heterocycles to generate unknown 3,5-disubstituted thiadiazole derivatives.

An efficient method for the preparation of N-formyl imide via amidine using propylphosphonic anhydride (T3P®) has been described. Using this method many aryl, hetero aryl, alkyl as well as amino acid imides were synthesized in high yields.

A series of 2,5-disubstituted-1,3,4-thiadiazole derivatives 5a-5l, 7a-7e and 9 have been synthesised and screened for in vitro antimycobacterial activity against Mycobacterium smegmatis MC-155. In addition these compounds have also been screened for cytotoxic activity against cancer cell lines HT-29, MDA-MB-231 by MTT colorimetric assay. The compounds are well characterized by spectral analysis viz. (1)H NMR, (13)C NMR, FT-IR, mass and HRMS. Screening results indicate that compounds 5g, 7a possess good antitubercular activity with MIC value 65.74 and 40.86, respectively, compounds 5g, 7a, 7b, 7d, 7e and 9 displayed promising cytotoxic activity against the cell lines tested. 5g and 7a stand out to be potent antimycobacterial and anticancer agents among the tested series. Further the title compounds were also tested on human normal cells HEK293T and are found to be safer with lesser cytotoxicity. It is interesting to observe that compound 5g has come out to be safer, potent anticancer and antimycobacterial agent.

A new series of isoxazole tethered quinone-amino acid hybrids has been designed and synthesized involving 1,3-dipolar cycloaddition reaction followed by an oxidation reaction using cerium ammonium nitrate (CAN). Using this method, for the first time various isoxazole tethered quinone-phenyl alanine and quinone-alanine hybrids were synthesized from simple commercially available 4-bromobenzyl bromide, propargyl bromide, and 2,5-dimethoxybenzaldehyde in good yield.

A new synthesis of pyrazolo[4,3-d]pyrimidines and isoxazolo[4,5-d]pyrimidines is described. Key steps in the synthesis involve Stille coupling of 4,6-dichloro-2-phenyl-pyrimidine with tributyl(1-ethoxyvinyl)stannane and tandem Schiff-base formation/heterocyclization of 2,6-di-aryl-5-fluoro-4-acetylpyrimidine with hydrazines or ­hydroxylamine to give pyrazolo[4,3-d]pyrimidines and isoxazolo[4,5-d]pyrimidines, respectively. The position of the fluoro group in the ­pyrimidine ring is important for the success of heterocylization reaction.

An efficient method for the preparation of N-formyl imide via amidine using propylphosphonic anhydride (T3P®) has been described. Using this method many aryl, hetero aryl, alkyl as well as amino acid imides were synthesized in high yields.

A series of novel diaziridinyl quinone isoxazole hybrids (9a-9j) were synthesized starting from 2, 5-dimethoxy acetophenone 1 via Claisen reaction, cyclisation, alkoxy carbonylation, hydrolysis, oxidation and aziridine insertion. All the compounds were screened for antimicrobial, anti-biofilm and cytotoxic activities. Among the screened compounds, the compound 9h showed good antibacterial and anti-biofilm activities with MIC value of 3.9, 3.9, 3.9 and 7.8 μg/mL, respectively, and IC50 values of 1.9, 2.5, 2.8 and 5.1 μM, respectively, against Staphylococcus aureus MTCC 96, S. aureus MLS-16 MTCC 2940, Bacillus subtilis MTCC 121 and Klebsiella planticola MTCC 530, and also exhibited potent antifungal activity against Candida albicans MTCC 227, C. albicans MTCC 854 and Candida krusei MTCC 3020 equipotent to standard miconazole (MIC value 7.8 μg/mL). All the synthesized compounds exhibited promising cytotoxicity against A549 and PC3 cell lines (IC50 values between 1 and 4 μM). Compounds 9b and 9j exhibited IC50 value of 0.5 μM which was similar to that of Mitomycin C against PC3 cell line.

An efficient method for the preparation of novel 2-(5-arylisoxazol-3-yl)cyclohexa-2,5-diene-1,4-dione hybrids via 1,3-dipolar cycloaddition followed by an oxidation reaction using ceric ammonium nitrate (CAN) has been described. Using this method, various aryl as well as alkyl substituted isoxazole-benzoquinone hybrids were synthesized in high yields.

An efficient method for the preparation of kojic acid based α-amino acid derivatives by alkylation of glycinate schiff base with bromokojic acids have been described. Using this method, mono as well as di alkylated kojic acid-amino acid conjugates have been prepared. This is the first synthesis of C-linked kojic acid-amino acid conjugate where kojic acid is directly linked to amino acid through a C-C bond.

Various substituted oxazolidin-2-ones were synthesized from the corresponding amino alcohols using ethyl imidazole-1-carboxylate (EImC). Highly substituted and sterically hindered amino alcohols an...

β-Hydroxy ketones were synthesized in one-pot from β-diketones by reducing alkyl ketones chemoselectively by keeping aryl ketone intact. Initially, β-diketones were enolized using LiHMDS and later alkyl ketone was chemoselectively reduced efficiently by lithium aluminium hydride. This method produces β- hydroxyl ketones from the corresponding β-diketones in high yield.

An efficient method for the synthesis of mono α-aryl derivatives of diethyl malonate and ethyl cyanoacetate using ethyl-1-imidazole carbamate (EImC) has been described. Using this method many sterically hindered and highly substituted mono α-aryl derivatives of diethyl malonate and ethyl cyanoacetate were synthesized in high yield.

Various substituted oxazolidin-2-ones were synthesized from the corresponding amino alcohols using ethyl imidazole-1-carboxylate (EImC). Highly substituted and sterically hindered amino alcohols an...

1,3-Dipolar cycloaddition of nitrile oxides derived from oximes of type (I) with terminal alkynes and following oxidative demethylation offers a regioselective synthesis of isoxazole substituted p-benzoquinones (IV) (10 examples).

A simple approach to the title compounds, which are required as synthons of heterocycles, becomes possible by treatment of arylacetic esters (II) and nitriles (IV) with reagent (I).