27439-08-3Relevant articles and documents
Ruthenium-Catalyzed Dynamic Kinetic Resolution Asymmetric Transfer Hydrogenation of β-Chromanones by an Elimination-Induced Racemization Mechanism
Ashley, Eric R.,Sherer, Edward C.,Pio, Barbara,Orr, Robert K.,Ruck, Rebecca T.
, p. 1446 - 1451 (2017)
Chiral chroman derivatives are important pharmacophores in natural and synthetic bioactive molecules. The discovery of catalytic asymmetric methods for the synthesis of these compounds is an important goal. Ruthenium-catalyzed asymmetric transfer hydrogenation under strongly basic conditions has been found to induce dynamic kinetic resolution of β-substituted chromanones, producing valuable chromanols in high yields and with high levels of stereocontrol. The reaction proceeds by base-catalyzed racemization of the β-stereocenter through a conjugate elimination/conjugate addition pathway in concert with a highly selective ketone transfer hydrogenation step. Computational analysis of the catalyst, substrate, and transition state structures has revealed the driving interactions for diastereoselectivity as well as unexpected CH-O stabilizing interactions between the catalyst sulfonamide and the reacting substrate.
Stereoselective reduction of flavanones by marine-derived fungi
Birolli, Willian G.,Nitschke, Marcia,Porto, André Luiz M.,Santos, Darlisson de A.,de Matos, Iara L.
, (2021/08/13)
Biotransformation is an alternative with great potential to modify the structures of natural and synthetic flavonoids. Therefore, the bioreduction of synthetic halogenated flavanones employing marine-derived fungi was described, aiming the synthesis of flavan-4-ols 3a-g with high enantiomeric excesses (ee) of both cis- and trans-diastereoisomers (up to >99% ee). Ten strains were screened for reduction of flavanone 2a in liquid medium and in phosphate buffer solution. The most selective strains Cladosporium sp. CBMAI 1237 and Acremonium sp. CBMAI1676 were employed for reduction of flavanones 2a-g. The fungus Cladosporium sp. CBMAI 1237 presented yields of 72–87% with 0–64% ee cis and 0–30% ee trans with diastereoisomeric ratio (dr) from 52:48 to 64:36 (cis:trans). Whereas Acremonium sp. CBMAI 1676 resulted in 31% yield with 77–99% ee of the cis and 95–99% ee of the trans-diastereoisomers 3a-g with a dr from 54:46 to 96:4 (cis:trans). To our knowledge, this is the first report of the brominated flavon-4-ols 3e and 3f. The use of fungi, with emphasis for these marine-derived strains, is an interesting approach for enantioselective reduction of halogenated flavanones. Therefore, this strategy can be explored to obtain enantioenriched compounds with biological activities.
Organocatalytic Approach for Assembling Flavanones via a Cascade 1,4-Conjugate Addition/oxa-Michael Addition between Propargylamines with Water
He, Xinwei,He, Xinwei,Xie, Mengqing,Li, Ruxue,Choy, Pui Ying,Tang, Qiang,Shang, Yongjia,Kwong, Fuk Yee
, p. 4306 - 4310 (2020/06/05)
A DBU-catalyzed one-pot cascade reaction of propargylamines and water for the synthesis of flavanones has been developed. This process proceeds via a sequence of 1,4-conjugate addition of water to alkynyl o-quinone methide (o-AQM), followed by the alkyne-allene isomerization and subsequent intramolecular oxa-Michael addition. This strategy provides a convenient method for accessing a broad range of flavanones in good to excellent yields with good functional-group tolerance, in particular, the reactive halo functional groups.
