An uhexpected success involving the rearrangement of N-benzoyl2-pyrrolidone(1)to 2-phenylpyrroline (2)1 provided us with an imaginative heuristic upon which some novel entries into the pyrrolidine and piperdine alkaloids was based. 相似文献
A concise and efficient total synthesis of (-)-umbelactone 1, an occurring γ-hydroxymethyl-α, β-butenolide from Memycelon umbelatum Burro, is described. The synthesis features the use of a ring closing metathesis strategy. 相似文献
Previous work in our laboratory was around the development of chiral 2-pyrrolidinone synthon A. Malimides 1 and 2, which can be easily prepared from (S)-malic acid, have been shown to be versatile chiral synthetic intermediates. All the reactivities showed in synthon A have been exploited.1 相似文献
Continuous flow synthetic technologies had been widely applied in the total synthesis in the past few decades. Fully continuous flow synthesis is still extremely focused on multi-step synthesis of complex natural pharmaceutical molecules. Thus, the development of fully continuous flow total synthesis of natural products is in demand but challenging. Herein, we demonstrated the first fully continuous flow approach towards asymmetric total synthesis of natural tetrahydroprotoberberine alkaloids, (−)-isocanadine, (−)-tetrahydropseudocoptisine, (−)-stylopine and (−)-nandinine. This method features a concise linear sequence involving four chemical transformations and three on-line work-up processing in an integrated flow platform, without any intermediate purification. The overall yield and enantioselectivity of this four-step continuous flow chemistry were up to 50 % and 92 %ee, respectively, in a total residence time of 32.5 min, corresponding to a throughput of 145 mg/h. 相似文献
In this study, bergapten was synthesized in a yield of 55% from phloroglucinol as starting material, via a novel approach including monomethylation, Hoesch reaction, acetylation, deacetoxylation, Pechmann condensation and 2,3-dichloro-5,6- dicyano-1,4-benzoquinone(DDQ) dehydrogenation. With the adoption of the acetylation of enol tautomer, the deacetoxylation and the DDQ dehydrogenation, the novel approach differs greatly from the processes reported previously, though the starting material was the same or similar to those used on previous synthetic processes. The newly adopted reaction underwent easily, affording all reactions in high yields, especially acetylation and deacetoxylation and DDQ dehydrogenation in almost quantitative yields, ensuring a final yield higher than those previously reported. 相似文献
An inexpensive proline derivative and chiral control feature in the total synthesis of securinega alkaloids (-)-norsecurinine (1) and phyllanthine (2). Key steps in the synthesis of 1 include an intramolecular ketonitrile coupling and application of a radical-based generation of N-acylimines. The total synthesis of 2 utilizes a stereoselective imino Diels - Alder construction of the methoxypiperidine ring. 相似文献
The absolute configuration of 3-methylpyrrolidine alkaloids isolated from the poison gland of ants Leptothoracini was determined as (3R). The enantiomeric separation by chiral gas chromatography and unambiguous structural assignment of the target compounds are described. 相似文献
Voilà, optical activity : Both enantiomers of 1‐chloroindene have been synthesized in high selectivity from solely achiral starting materials, and without using optically active catalysts (see scheme). These symmetry‐breaking syntheses provide a proof‐of‐concept for a new approach to asymmetric synthesis. NCS=N‐chlorosuccinimide.
A new protocol based on a palladium-catalyzed Heck reaction of an amino acid–derived vinyl unit with 3-bromoquinoline has been developed to access the title compounds in good yield and optical purity. 相似文献
A new bondset for cortical steroid synthesis is developed from the dual concepts of convergent assembly and multiple construction. A short synthesis on this bondset is presented in which the final bond construction by electrocyclization took an unwanted course. Stereocontrol is discussed separately. 相似文献
Amaryllidaceae alkaloids appeal to organic chemists with their attractive structures and their impressive antitumor and acetylcholinesterase inhibitory properties. We demonstrate a highly versatile access to this family of natural products. A general protocol with high yields in a sustainable electro-organic key transformation on a metal-free anode to spirodienones facilitates functionalization to the alkaloids. The biomimetic syntheses start with the readily available, inexpensive biogenic starting materials methyl gallate, O-methyl tyramine, and vanillin derivatives. Through known dynamic resolutions, this technology provides access to both enantiomeric series of (epi-)martidine, (epi-)crinine, siculine, and galantamine, clinically prescribed for the treatment of Alzheimer's disease. 相似文献
1,2-Dithienylethanediones were synthesized by modified acylation of thiophene and its homologs in the presence of aluminum chloride and pyridine. The bishydrazones of the products were converted into dithienylacetylenes by oxidation with atmospheric oxygen in pyridine in the presence of CuCl. 相似文献
6-acetamido-6,8-dideox-1,2:3,4-di-O-isopropylidene-D-glycero-α-D-galacto-octopyranos-7-ulose (6), has been synthesised from D-galactose. The side chain elongation was carried out by cyano-amination of the protected dialdo sugar (2), followed by N-acetylation, and a subsequent Grignard reaction. 相似文献