查看更多>>摘要：? 2021 Elsevier LtdA synthesis of the BC ring moiety of brachialactone, a fusicoccane-type diterpene isolated from the tropical forage grass Brachiaria humidicola and found to inhibit nitrification by soil microbes, is described. Several precursors including the C ring were synthesized from a known chiral cyclopentane, and then subjected to the conditions for the Mizoroki-Heck reaction. Substrates incorporating vinyl (R = H) or enone (R = COCH3) moieties and incorporating an S configuration at C-2 successfully underwent intramolecular Mizoroki-Heck reaction, giving the BC ring structure of brachialactone.
查看更多>>摘要：? 2021 Elsevier LtdAn efficient 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ)-mediated oxidative coupling reaction of N,N-dimethyl enaminones with cycloheptatriene is developed. It provides a variety of α-alkenylated 1,3-dicarbonyl compounds in moderate to good yields under mild conditions.
查看更多>>摘要：? 2021 Elsevier LtdPerillene is an essential ingredient in a Chinese patent drug and features some fascinating biological activities. We present herein an efficient pathway to perillene that hangs on the cross-coupling reaction of allylic carbonates with furfuryl Grignard reagent catalyzed by Li2CuCl4. The synthetic applications of this transformation were demonstrated by the synthesis of analogical natural products dendrolasin, ambliofuran and thioperillene.
查看更多>>摘要：? 2021 The Author(s)During our studies into preparing analogues of pyrazolopyrimidine as ATP synthesis inhibitors of Mycobacterium tuberculosis, a regiospecific condensation reaction between ethyl 4,4,4-trifluoroacetoacetate and 3-(4-fluorophenyl)-1H-pyrazol-5-amine was observed which was dependent on the specific reaction conditions employed. This work identifies optimized reaction conditions to access either the pyrazolo[3,4-β]pyridine or the pyrazolo[1,5-α]pyrimidine scaffold. This has led to the structural confirmation of the previously reported pyrazolopyrimidine 17b which was reported as pyrazolo[1,5-α]pyrimidine structure 2 which was corrected to pyrazolo[3,4-β]-pyrimidine 19.
查看更多>>摘要：? 2021 Elsevier LtdNatural products with heterocyclic core units are ample and widespread in nature, with many compounds exhibiting promising therapeutic properties. Penipanoid A (1) is a triazole based natural product isolated from the marine sediment derived fungus Penicillium Aneum SD-44 and exhibits the cytotoxicity and antimicrobial activity. Structurally, it features a 1,2,4-triazole motif. Herein, we report an efficient total synthesis of Penipanoid A (1) by a multi-component reaction involving formation of a triazole ring system as the key fragment starting from 4-methoxyphenyl acetic acid. Deprotection of the methoxy protected compound 2 provided the required natural product 1.
查看更多>>摘要：? 2021 Elsevier LtdSelective photooxidation of alkyl benzenes was studied in a custom-built continuous flow photochemical reactor equipped with fine bubble generator and a low power UV light source. Fine bubbles of air were used as an oxidizing agent along with water-soluble sodium anthraquinone sulfonate as catalyst. The fine bubble containing slug-flow system using air was 1.4 times more efficient at lower feed-flow rate of 2 mL/min and 1.8 times more efficient at higher feed-flow rate of 5 mL/min. Ethylbenzene was selectively oxidized in continuous flow to acetophenone at room-temperature, with 90% ethylbenzene conversion and 92% selectivity to acetophenone, with a short residence time of 5 min. The enhanced gas/liquid mass transfer afforded by the fine bubble generator significantly increased reactor productivity, giving rise to high conversion and yield. Due to enhanced mass transfer and greater efficiency, compressed air can be used as oxidant instead of pure O2, thus alleviating potential safety concerns and making the process safer and more amenable for scale up.
查看更多>>摘要：? 2021 Elsevier LtdAn efficient and practical protocol for the Oxone?-mediated halocyclization/demethylation of 2-alkynylthioanisoles towards valuable 3-halobenzo[b]thiophenes is described. Structurally diverse 3-halobenzothiophenes were obtained in good to excellent yields under mild reaction conditions.
查看更多>>摘要：? 2021 Elsevier LtdAn efficient electrochemical synthesis of 1,2,3-trisubstituted pyrroles was developed by one-pot three-component reaction of β-dicarbonyl compounds, aldehydes with amines. The target products could be obtained in good to excellent yields. Our investigations indicate that β-enamino ketone is a key intermediate in this transformation and the reaction mechanism may involve a radical addition reaction pathway.
查看更多>>摘要：? 2021 Elsevier LtdDesmosine is an elastin crosslinking amino acid that is expected to be a useful biomarker of diseases related to elastin degradation including chronic obstructive pulmonary disease (COPD). In this study, conjugates of desmosine and carrier proteins, such as bovine serum albumin (BSA) and keyhole limpet hemocyanin (KLH), with linkers were designed and prepared for the creation of an effective antibody to be used in the development of an enzyme-linked immunosorbent assay (ELISA) system. Synthesis of desmosine along with the linkers having appropriate lengths was achieved via stepwise and chemo/regioselective palladium-catalyzed Sonogashira and Negishi cross-coupling reactions starting from an alkyne with protecting groups over nine steps. Subsequently, Michael addition with a thiolated carrier protein (BSA/KLH) was carried out using Traut's reagent to afford seven types of desmosine-BSA/KLH conjugates.
查看更多>>摘要：? 2021 Elsevier LtdHere, we describe the synthesis and properties of BMeS-p-A-NHS as a sulfonylaniline-based fluorescent labeling reagent. Introduction of a carboxyl group into the amino group of the sulfonylaniline skeleton was achieved by the ring-opening reaction of β-propiolactone. This small labeling reagent was water-soluble, photostable, solid-state emissive, and suitable for excitation with a versatile 405-nm laser diode, emitting green fluorescence with a large Stokes shift at 527 nm. The succinimidyl ester reactive group facilitated conjugation with substrates containing amino groups.
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