DDQ-mediated Direct Intramolecular-Dehydrogenative-Coupling (IDC): Expeditious Approach to the Tetracyclic Core of Ergot Alkaloids
摘要:
An efficient route to 2-oxindoles bearing an all-carbon quaternary center at the pseudobenzylic position has been developed via a DDQ-mediated Intramolecular-Dehydrogenative-Coupling (IDC). The methodology involves a one-pot C-alkylation of beta-N-arylamido esters (7) concomitant with dehydrogenative-coupling in the presence of stoichiometric amount of DDQ. A tentative mechanistic route has been proposed for the oxidative coupling. The methodology provides a two-step entry to the ergoline structure of ergot alkaloids.
Stereoselective Metal-Free Synthesis of β-Amino Thioesters with Tertiary and Quaternary Stereogenic Centers
作者:Annette Bahlinger、Sven P. Fritz、Helma Wennemers
DOI:10.1002/anie.201310532
日期:2014.8.11
β‐Amino thioesters are important natural building blocks for the synthesis of numerous bioactive molecules. An organocatalyzed Mannich reaction was developed which provides direct and highly stereoselective access to acyclic β2‐ and β2,3,3‐amino thioesters with adjacent tertiary and quaternary stereocenters. Mechanistic studies showed that the stereochemical course of the reaction can be controlled
benzylic position has been achieved via a 'transition-metal-free' intramolecular dehydrogenative coupling (IDC). The construction of 2-oxindole moieties was carried out through formation of carbon-carbon bonds using KOt-Bu-catalyzed one pot C-alkylation of beta-N-arylamido esters with alkyl halides followed by a dehydrogenative coupling. Experimental evidences indicated toward a radical-mediated path for
with carbodiimides to form the corresponding substituted ketenes that can react in situ with alcohols providing esters in a high yield. The ketene formed by the treatment of ethyl 2-methylmalonate with DCC was trapped in situ by a [4+2] cycloaddition with a second DCC molecule. The chemoselectivity of the acylation through the keteneintermediates was found to be substantially different from that of conventional
Quaternized α,α′-Amino Acids via Curtius Rearrangement of Substituted Malonate–Imidazolidinones
作者:Maheswara Rao Gokada、Roger Hunter、Ana Andrijevic、Wade F. Petersen、Sauvik Samanta、Gerhard Venter、Sophie Rees-Jones
DOI:10.1021/acs.joc.7b01684
日期:2017.10.6
An efficient synthesis protocol is presented for accessing quaternized α-amino acids in chiral, nonracemic form viadiastereoselective malonate alkylation followed by C- to N-transposition. The key stereodifferentiating step involves a diastereoselective alkylation of an α-monosubstituted malonate–imidazolidinone, which is followed first by a chemoselective malonate PMB ester removal and then a Curtius
2-Phenylimidazo[2,1-b]benzothiazole compounds, salts thereof, process of
申请人:Yamanouchi Pharmaceutical Co., Ltd.
公开号:US04464384A1
公开(公告)日:1984-08-07
Novel 2-phenylimidazo[2,1-b]benzothiazole compounds shown by general formula I ##STR1## and the salts thereof, a process of producing the compounds, and pharmaceutical compositions containing the compounds. The compounds of this invention act on immune response, in particular, suppress a delayed type hypersensitivity reaction, and are useful as antiallergic agents, antirheumatics, therapeutic agents for autoimmune diseases, and suppressants of rejection at tissue transplantation and skin graft.