10.1016/S0957-4166(96)00463-6
The study focuses on the efficient synthesis of two camphor-derived chiral controllers, (2R-exo)-10-methylthio-2-bornanethiol (lb) and (2R-exo)-2,10-bis(methylthio)bornane (2), which have potential applications as ligands or chiral auxiliaries in asymmetric synthesis. The key starting material is (1S)-camphor-10-thiol (3), which is converted through a series of reactions involving benzoyl chloride, Lawesson's reagent, lithium aluminum hydride (LiAlH4), and diisobutylaluminum hydride (DIBAL-H) to achieve the desired chiral compounds. The study highlights the stereoselective reduction of thiones as a crucial method for introducing sulfur functionality in position 2 of the camphor-derived compounds. The synthesized compounds are characterized by various spectroscopic techniques, and their potential use in catalytic asymmetric hydroformylation and Pauson-Khand reactions is discussed.
10.1039/b702411h
The study presents a concise synthetic route to the anti-cancer agents combretastatin A-4 and DMU-212 using the Ramberg–B?cklund reaction. Combretastatin A-4, isolated from the African tree Combretum caffrum, is a potent inhibitor of tubulin polymerization, while DMU-212 is a synthetic analogue with cancer chemoprotective activity. The synthesis of combretastatin A-4 begins with the coupling of thiol 13, prepared from 3,4,5-trimethoxybenzyl alcohol using Lawesson’s reagent, and bromide 14, using potassium hydroxide in ethanol. The resulting sulfide is oxidized with m-chloroperoxybenzoic acid to form sulfone 12. The Ramberg–B?cklund reaction, carried out under various conditions (Meyers, Chan, and Franck), converts sulfone 12 into the stilbene intermediate 15, which is then desilylated to yield combretastatin A-4. The study also explores the synthesis of other combretastatin analogues, including (E)- and (Z)-2012, using similar procedures. The Ramberg–B?cklund reaction is further applied to prepare DMU-212 from sulfone 29, derived from 4-methoxybenzyl mercaptan and bromide 17. The study highlights the efficiency and stereoselectivity of the Ramberg–B?cklund reaction in synthesizing these anti-cancer stilbenes and provides insights into the reaction's scope and limitations.
10.1055/s-2005-918433
The research aims to develop an efficient synthesis of novel 8-trifluoromethyl-7H-thiazolo[3,2-b]- and 1,2,4-triazolo[4,3-b]pyridazines, which are potentially biologically active compounds. The study builds on the known pharmacological properties of 6-aryl-1,2,4-triazolo[4,3-b]pyridazine derivatives, such as their anxiolytic and antihypertensive effects, and explores the impact of incorporating a trifluoromethyl group at a unique position on these molecules. The synthesis starts from 4-trifluoromethyl-4,5-dihydropyridazin-3-one, using a five-membered ring closure strategy involving bis(electrophilic) reagents reacting with exocyclic and endocyclic nucleophilic centers on the pyridazine nucleus. Key chemicals include Lawesson’s reagent for thionation, methyl α-bromoacetate for ring closure, and various reagents like phosphorous oxy chloride and hydrazine for further functional group transformations. The study concludes that the synthesized compounds, such as 4, 8, 9, and 10a/b, can be efficiently accessed under mild conditions and are promising candidates for further biological evaluation due to their unique structure and potential for chemical transformations.
10.3987/COM-90-5442
The study detail the first synthesis of thienotriazolothiazepines, a novel heteroazepine derivative with anti-PAF (platelet activating factor) activity. The researchers synthesized these compounds to explore their potential as potent and orally active PAF antagonists. The synthetic route involved several steps, including the formation of 2-aminothiophenes, protection and reduction of amino groups, Mitsunobu conditions to form sulfides, hydrolysis to carboxylic acids, cyclization to form thiazepine rings, and the construction of triazole rings using Lawesson's reagent and subsequent treatments with hydrazine monohydrate and trimethyl orthoacetate. The synthesized thienotriazolothiazepines were tested for their ability to inhibit rabbit platelet aggregation induced by PAF, and all compounds exhibited anti-PAF activity. The study concludes that the synthesized compounds are effective in inhibiting PAF-induced platelet aggregation, suggesting their potential as therapeutic agents for conditions related to platelet aggregation.
10.1002/jccs.199600014
The study focuses on the synthesis of novel triazole, sulfur-containing diazole, and N-phenylthiatriazole biphenyltetrazole derivatives as potential angiotensin II receptor antagonists. This research was inspired by the success of the angiotensin II receptor antagonist losartan (DuP 753) and aimed to explore alternative heterocycles that could maintain or enhance its efficacy. Chemicals such as methyl valerimidate hydrochloride, thionyl chloride, N-methylmorpholine, cesium carbonate, and Lawesson's reagent were used in the synthetic processes. Among the synthesized compounds, 5-butyl-3-[(2-trifluoromethyl)phenyl]-2,1,3,4-1H-thiatriazole-2-one biphenyltetrazole demonstrated promising in vitro activity, suggesting its potential for further pharmaceutical development?.
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