Oxobenzo[f]benzopyrans as new fluorescent photolabile protecting groups for the carboxylic function

The properties of three oxobenzo[f]benzopyrans as new fluorogenic photolabile protecting groups for the carboxylic function of amino acids were studied. Fluorescent amino acid conjugates were efficiently prepared and characterised. Photodeprotection of these compounds was carried out by irradiation at 300, 350 and 419 nm, the most suitable wavelength being 350 nm, on account of short irradiation times and good deprotection yields.     

One‐Pot Synthesis of 2‐Amino‐4‐aryl‐3‐carbalkoxy‐7,7‐dimethyl‐5,6,7,8‐tetrahydrobenzo[b]pyran Derivatives Catalyzed by KF/Basic Al2O3 Under Ultrasound Irradiation

Abstract

Synthesis of 2‐amino‐4‐aryl‐3‐carbalkoxy‐7,7‐dimethyl‐5‐oxo‐5,6,7,8‐tertrahydrobenzo[b]pyran derivatives was carried out in 81–98% yields by one‐pot condensation of aromatic aldehydes with cyanoacetic esters and 5,5‐dimethyl‐1,3‐cyclohexanedione catalyzed by KF/basic Al₂O₃ at room temperature under ultrasound irradiation.     

Efficient and general method for the synthesis of benzopyrans by ethylenediamine diacetate-catalyzed reactions of resorcinols with α,β-unsaturated aldehydes. One step synthesis of biologically active (±)-confluentin and (±)-daurichromenic acid

An efficient and general synthesis of benzopyrans is achieved by ethylenediamine diacetate-catalyzed reactions of resorcinols with α,β-unsaturated aldehydes in moderated yields. As an application of this methodology, biologically interesting confluentin, which was known to have an inhibitory effect on histamine release is synthesized in one step. Also, natural daurichromenic acid, which has highly potent anti-HIV activity, is successfully synthesized in one step.     

钾通道启开剂研究(Ⅰ)─—反式-4-氨基-3-羟基-3,4-二氢-2,2-二甲基-2-氢-1-苯并吡喃类化合物的合成及其心血管活性

通过溴醇两步环氧化法并采用三本基膦脱氧合成了一系列新型的反式－4－氨基－3－羟基-3，4－二氢－2，2－二甲基－2－氢－1－苯并吡喃类化合物，通过IR、NMR、MS和元素分析等手段对其结构进行了确证．研究了其中13个化合物对KCI刺激大鼠胸主动脉条收缩抑制作用，考察了其体外血管扩张活性；还对其中11个化合物进行了S．D．大鼠体内降血压实验．结果表明，所测化合物对低钾刺激引起的收缩均有不同程度的抑制作用，其中化合物Ⅰ1、Ⅰ2、Ⅱ5、Ⅱ6效果较好，部分化合物显示较好的降血压活性．     

Synthesis of Functionalized Benzopyrans via Intramolecular 1,3-Dipolar Cycloaddition of Nitrile Oxides

Various functionalized benzopyran derivatives have been synthesized in good yields by a sequence of reactions viz. intramolecular cyclization of nitrile oxides, reductive cleavage, and acetylation.     

Synthesis of functionalized benzopyrans by sequential [3+3]-cyclization—Williamson reactions of 1,3-bis(trimethylsilyloxy)-7-chlorohepta-1,3-dienes

Functionalized benzopyrans were regioselectively prepared by [3+3]-cyclization of 1,3-bis(trimethylsilyloxy)-7-chlorohepta-1,3-dienes with 3-silyloxy-2-eno-1-ones and subsequent intramolecular Williamson reactions of the salicylates thus formed.     

A New Isofuranonaphthalenone and Benzopyrans from the Endophytic Fungus Nodulisporium sp. A4 from Aquilaria sinensis

A new isofuranonaphthalenone, (7R*,8S*)‐3,6,7,8‐tetrahydro‐4,7,8‐trihydroxynaphtho[2,3‐c]furan‐5(1H)‐one ( 1 ), and a new benzopyran, (2R*,4R*)‐3,4‐dihydro‐4‐methoxy‐2‐methyl‐2H‐1‐benzopyran‐5‐ol ( 2 ), together with four known related analogs, 3 – 6 , were isolated from the culture of Nodulisporium sp. A4, an endophytic fungus from the stem of Aquilaria sinensis (Lour.) Gilg . The structures of the isolated compounds were determined by extensive analysis of their spectroscopic data as well as by comparison with literature reports. The isolated compounds 1 – 6 were evaluated for their cytotoxic activities against the NCI‐H460 and SF‐268 tumor cell lines.     

3-Iodo-4-chalcogen-2H-benzopyran as a convenient precursor for the sonogashira cross-coupling: synthesis of 3-alkynyl-4-chalcogen-2H-benzopyrans

3-Iodo-4-chalcogen-2H-benzopyran derivatives underwent a direct Sonogashira cross-coupling reaction with several terminal alkynes in the presence of a catalytic amount of Pd(PPh₃)₂Cl₂ with CuI as a co-catalyst, using Et₃N as base and solvent. This cross-coupling reaction proceeded cleanly under mild conditions and was performed with propargylic alcohols, propargylic ethers, as well as alkyl and aryl alkynes, furnishing the correspondent 3-alkynyl-4-chalcogen-2H-benzopyrans in good yields.     

Two New Endiandric Acid Analogs,a New Benzopyran,and a New Benzenoid from the Root of Beilschmiedia erythrophloia

Phytochemical investigation of the root of Beilschmiedia erythrophloia led to the isolation and structural elucidation of two new endiandric acid analogs, endiandric acids I and J ( 1 and 2 , resp.), a new benzopyran, dehydrooligandrol methyl ether ( 3 ), and a new benzenoid, farnesylol ( 4 ), together with six known compounds. Their structures were established on the basis of extensive 1D‐ and 2D‐NMR analyses in combination with HR‐MS experiments.     

A one-pot [Bmim]OH-mediated synthesis of 3-benzamidocoumarins

The first example of an ionic liquid-promoted one-pot synthesis of 3-benzamidocoumarins from salicylaldehydes and 2-pheny-1,3-oxazolan-5-one via Knoevenagel condensation-ring transformation cascades has been reported. No by-product formation, operational simplicity, ambient temperature and high yield (85-97%) are the salient features of the present synthetic protocol. After isolation of the product, the ionic liquid, [Bmim]OH can be easily recycled for further use without any loss of efficiency.