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Tyrosinase is a copper‐containing enzyme involved in the biosynthesis of melanin pigment. While the excess production of melanin causes hyperpigmentation of human skin, hypopigmentation results in medical conditions like vitiligo. Tyrosinase inhibitors could be used as efficient skin whitening agents and tyrosinase agonists could be used for enhanced melanin synthesis and skin protection from UV exposure. Among a wide range of tyrosinase‐regulating compounds, natural and synthetic derivatives of furochromenones, such as 8‐methoxypsoralen (8‐MOP), are known to both activate and inhibit tyrosinase. We recently reported a synthetic approach to generate a variety of dihydrofuro[3,2‐c]chromenones and furo[3,2‐c]chromenones in a metal‐free condition. In the present study, we investigated these compounds for their potential as antagonists or agonists of tyrosinase. Using fungal tyrosinase‐based in vitro biochemical assay, we obtained one compound (3k) which could inhibit tyrosinase activity, and the other compound (4f) that stimulated tyrosinase activity. The kinetic studies revealed that compound 3k caused 'mixed' type tyrosinase inhibition and 4f stimulated the catalytic efficiency. Studying the mechanisms of these compounds may provide a basis for the development of new effective tyrosinase inhibitors or activators. [ABSTRACT FROM AUTHOR]

Herein, DFT studies corroborating experimental results revealed that the shortest intramolecular hydrogen bonding distance of cis/trans‐oxaphosphetane (OPA) oxygen with the CH‐hydrogen of a triphenylphosphine phenyl ring provides good evidence for the attained olefin Z/E‐selectivity in Wittig olefination of the studied examples. 2‐Nitrobenzaldehyde, 3‐nitrobenzaldehyde, 2‐nitro‐3‐bromobenzaldehyde, 2‐nitro‐5‐bromobenzaldehyde and 2‐nitro‐5‐arylbenzaldehydes provided Z‐nitrostilbenes with (2‐chloro‐4‐hydroxy‐3‐methoxy‐5‐(methoxycarbonyl)benzyl) triphenylphosphonium chloride as the major products. However, 4‐nitrobenzaldehyde and 2‐nitro‐6‐bromobenzaldehydes furnished E‐nitrostilbenes as the major products in high yields. Furthermore, the DFT computed intramolecular CH1/CH2‐hydrogen bond distances with Cl/NO2 of selected stilbene derivatives were in good agreement with intramolecular hydrogen bond distances measured from single‐crystal X‐ray diffraction measurements. [ABSTRACT FROM AUTHOR]

A facile one-step synthetic approach to dihydrofuro-[3,2- c ]chromenones and furo[3,2- c ]chromenones by the reaction of methyl enol ethers with 4-hydroxycoumarins under metal-free conditions is presented. Dihydrofuro[3,2- c ]chromenones and furo[3,2- c ]-chromenones were selectively obtained by controlling the stoichiometry of boron trifluoride diethyl etherate. An unexpected aryl-group migration followed by aromatization of the furan moiety, leading to a variety of furo[3,2- c ]chromenone derivatives in good yields, is reported. [ABSTRACT FROM AUTHOR]

The first total synthesis of acylphloroglucinol-based natural products faberiones A, B, and E is reported, which were isolated from Hypericum faberi. Total syntheses of faberiones A and B are accomplished in six linear steps from commercially accessible 1,3,5-trimethoxybenzene (methyl protected form of phloroglucinol) in overall yields of 31 and 33% respectively, via simple and straightforward approaches that include acylation, o-methoxy deprotection, selective iodination and tandem-Sonogashira cyclization followed by C-geranylation. Faberione E is achieved in two linear steps from acylphloroglucinol with an overall yield of 57% via geranylation followed by benzopyran formation reaction. [ABSTRACT FROM AUTHOR]

An efficient approach for synthesizing fused nitrogen containing heterocycles has been formulated. The approach relies on the use of 2-bromo-3-(arylamino)-1H-inden-1-one derivatives as precursors for the synthesis of indenoindoles and indenoisoquoinolines. The synthesis of indenoindoles is achieved via palladium-catalyzed C-H activation strategy, while a sequential palladium-catalyzed intermolecular Suzuki coupling followed by an intramolecular annulation process is used to synthesize indenoisoquinolines. The developed strategy offers indenone fused polycycles in moderate to good yields. [ABSTRACT FROM AUTHOR]

Background: Xanthogranulomatous pyelonephritis (XGP) is chronic pyelonephritis subtype where in renal parenchymal destruction occurs and therefore results in progressive loss of kidney functions. Although middle age group is the predominant age group affected but it can be seen at any age. There is accumulation of macrophages (lipid-laden) leading to renal parenchymal destruction and fibrosis. In this study, we present our data of 15 patients who had undergone nephrectomy and were biopsy proven XGP. Aims and Objectives: The aim of the study was to describe the clinical and radiological features of XGP in adults. Materials and Methods: XGP constituted 4.31% of the 348 nephrectomies done for infective causes over a period of 7 years. All our patients had undergone unilateral total nephrectomy. Demographic and clinical records were analyzed after consent from all the patients. Results: The age range in our study was 18–65 years with mean 42.93±15.66 years. Nine of our patients, that is, 60% were females. Diabetes was present in 53.3% of our patients. Three patients had imaging suggestive of pyonephrosis, three patients had perinephric collection and 9 patients (60%) had concomitant nephrolithiasis. All the kidneys were grossly enlarged and were non-functional on renal scintigraphy. Conclusion: XGP is a form of chronic pyelonephritis which although being less common but is devastating given the destruction of renal parenchyma it does and associated morbidity. Clinicoradiologic correlation cannot be overemphasized. The definitive diagnosis is established after histopathologic examination. [ABSTRACT FROM AUTHOR]

A stereoselective strategy for the replacement of the 1,2-dihaloalkene bridge of tetrahalonorbornyl derivatives by an oxygen bridge involving stepwise controlled oxidation, cleavage of the dione thus formed, and reiterative intramolecular S(sub N)2 displacement of two bridgehead halogens is devised. The synthesis of four highly strained pentacyclic bis-oxa-bridged derivatives with interesting structural variations is presented.

Research has been conducted on the gamma-lactone-fused cyclopentanoids. The effect of the tetrahalonorborene derivatives' structural flexibility and stereochemical control on these cyclopentannulated gamma-lactones has been investigated and the details are described.

The role of pi-allylpalladium intermediate in the organic synthesis is central to the palladium-catalyzed reactions of allenes with carbon and heteroatom nucleophiles. The application and reactivity of the pi-allylpalladium species in the synthesis of natural products using allenes and mechanistic aspects of reactions involved are discussed.

Alkyl enol ethers (AEE) are versatile synthetic intermediates with a unique reactivity pattern. This review article summarizes the synthesis of AEE as well as its reactivity and how enol ether undergoes intermolecular reactions for various bond formation, leading to the construction of several useful organic molecules. The synthetic applications of alkyl enol ethers towards intermolecular bond‐forming reactions include metal‐catalyzed reactions, cycloaddition and heterocycle formation as well as rwactions in the field of natural products synthesis. The achievement of these impressive transformations prove the countless synthetic potential of AEE. The main objective of this review is to bring attentiveness among synthetic chemists to show how AEE extensively can be used to react with both electrophiles as well as nucleophiles, thereby behaving as an ambiphilic reactant. We trust that the unique reactivity pattern of alkyl enol ethers and the fundamental mechanistic idea can attract chemists in AEE chemistry. Exclusively, intermolecular reactions of AEE with other functionalized moieties have not been reviewed to the best of our knowledge. [ABSTRACT FROM AUTHOR]

A simple computational model explains and predicts pi-facial selectivity in nucleophilic additions to sterically-free carbonyls. The model, based on MNDO, uses two sets of calculations. One measures electrostatic and polarization effects using a test charge to represent the nucleophile, while the other models the hydride ion to determine the added role of orbital interactions. Using these two, the approach is able to reproduce most empirically-established selectivities, especially with the hydride model.

Stereoselective formal synthesis of (_)-neplanocin A from a cyclopentane derivative is described by using an elegant strategy involving reiterative usage of an already existing acetonide protecting group. The acetonide protecting groups that is carried forward intact right from the starting adduct to an advanced intermediate is shuffled around twice as in a relay race through the synthetic sequence, which has avoided unnecessary employment of additional protecting groups.