Enantioselective synthesis of (+)-O-trimethylsappanone B and (+)-O-trimethylbrazilin
摘要:
The homoisoflavanoid (+)-O-trimethylbrazilin (1b) was prepared in 70% yield and 92% ee by acid-catalyzed rearrangement of O-trimethylsappanol (8) prepared by reduction of (R)-(-)-O-trimethylsappanone B (2b). The key step in the synthesis of (R)-(-)-2b is the reagent-controlled highly enantioselective hydroxylation (94%) of the sodium enolate of (+/-)-4-chromanone (3b) with the (+)-8,8-dichlorocamphorsulfonyl oxaziridine 7b.
Total Synthesis of (±)-Brazilin Using [4 + 1] Palladium-Catalyzed Carbenylative Annulation
作者:Vanessa Arredondo、Daniel E. Roa、Eugene S. Gutman、Nancy O. Huynh、David L. Van Vranken
DOI:10.1021/acs.joc.9b02343
日期:2019.11.15
in a formal synthesis of (±)-picropodophyllone and a totalsynthesis of (±)-brazilin. All prior syntheses of brazilin have involved a Friedel-Crafts alkylation in the key carbon-carbon bond forming events. The palladium-catalyzed [4 + 1] reaction generates a 1-arylindane with all of the functionalities needed for formation of the indano[2,1-c]chroman ring system of brazilin. The synthesis of (±)-brazilin
A concise synthetic approach to brazilin via Pd-catalyzed allylic arylation
作者:Youngeun Jung、Ikyon Kim
DOI:10.1039/c5ob00216h
日期:——
A short synthetic route to the trimethyl ether of brazilin was developed in 6 steps from 7-methoxychromene with 78% overall yield. Regioselective installation of a formyl group onto 7-methoxychromene followed by reduction and acetylation afforded allylic acetate. Palladium-catalyzedallylic coupling of allylic acetate with arylboronicacid provided direct access to 3-benzylchromene which was converted
Described herein is a highly efficient total synthesis of brazilin from commercially available starting materials in 9 steps with 70% overall yield. Mitsunobu coupling followed by In(III)-catalyzed alkyne-aldehyde metathesis allowed for rapid construction of brazilin core skeleton in quantitative yield. Subsequent modulation of oxidation levels and acid-catalyzed cyclization led to the trimethyl ether of brazilin. Asymmetric dihydroxylation of the key intermediate was also demonstrated, which would permit asymmetric access to (+)-brazilin.