Rapid Access to Tetracyclic Ring System of Lennoxamine Type Natural Product by Combined Use of a Novel Three-Component Reaction and Pummerer Cyclization.
A photoinduced sulfonylvinylation of unactivated C(sp3)-H bond through a three-component reaction of propargyl alcohols, potassium metabisulfite and cycloketone oxime esters is developed. This approach enables rapid access to cyanoalkylated vinyl...
α-Regio- and diastereoselective (3+2) cycloadditions of nitrone ylides derived from isatins with activated alkenes have been demonstrated. This mild protocol allows rapid access to a wide range of 3′,5′-diaryl-1′-hydroxy-2-oxospiro[indoline-3,2′-pyrrolidine] derivatives by using DABCO as an efficient catalyst. This method could also be carried out through three-component reaction efficiently in good yields and excellent diastereoselectivity.
AbstractThe enantioselective total synthesis of the alkaloid aristoquinoline has been achieved in seven steps and 26% overall yield. A new preparation of the useful synthetic building block (–)-α-terpinyl amine was also developed in order to avoid stoichiometric mercury reagents or azide-containing intermediates. Key steps in the optimized synthetic route include an intramolecular nitrilium ion cyclization to form the characteristic azabicyclo[3.3.1]nonane ring system and a diastereoselective reduction of the resulting imine mixture to afford the natural product. An isomer of aristoquinoline containing an exocyclic alkene was also obtained and found to exhibit unusual chromatographic and spectroscopic properties.
The synthesis of steroids and gaining an ultimate understanding of their reactivity was one of Sir Derek Barton’s most notable research areas. This highlight will focus on the construction of the steroid ring system from 2016 to 2018, and will include pathways that eventually led to natural product synthesis. For example, efficient syntheses of ent-pregnanolone sulfate and oestradiol methyl ether will be explained along with the total synthesis of cannogenol-3-O-α-l-rhamnoside.
A newly developed multicomponent reaction opens access to a variety of (poly)heterocyclic structures containing the underexplored skeleton of 1,3-thiazine-2-thione.
A three-component reaction for rapid access to underexplored 1,3-thiazine-2-thiones
