5162-64-1Relevant academic research and scientific papers
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.
Ruthenium-NHC-catalyzed asymmetric hydrogenation of flavones and chromones: General access to enantiomerically enriched flavanones, flavanols, chromanones, and chromanols
Zhao, Dongbing,Beiring, Bernhard,Glorius, Frank
, p. 8454 - 8458 (2013/09/02)
Two to four! Readily available flavones and chromones were efficiently converted into four valuable chiral classes of O-heterocycles - flavanones, chromanones, flavanols, and chromanols - by means of an enantioselective Ru/NHC-catalyzed hydrogenation process (see scheme; NHC=N-heterocyclic carbene, PCC=pyridinium chlorochromate). Copyright
Enantioselective acylation of (±)-cis-flavan-4-ols catalyzed by lipase from Candida cylindracea (CCL) and the synthesis of enantiopure flavan-4-ones
Ramadas, Sathunuru,Krupadanam, G.L. David
, p. 3381 - 3391 (2007/10/03)
Lipase Candida cylindracea (CCL) catalyzed acylation of (±)-cis-flavan-4-ols using vinyl acetate as the acyldonor in DME-toluene (1:2) gave (-)-(2R,4R)-4-acetoxyflavans 9a-m and (+)-(2S,4S)-flavan-4-ols 10a-m in high enantiomeric excess. (+)-(2S,4S)-Flava
REDUCTION OF 2'-HYDROXY CHALCONES UNDER PHASE TRANSFER CATALYSIS - A NEW METHOD FOR THE SYNTHESIS OF FLAVAN-4-OLS
Jyotsna, D.,Rao, A. V. Subba
, p. 1009 - 1014 (2007/10/02)
Reduction of 2'-hydroxy chalcones uner phase transfer catalysis conditions is discussed.The products are identified as 2,4-cis-flavan-4-ols.
Synthesis of Biflavonoids in which the Flavan Units are linked through Oxygen from C-2 to C-3 or C-4
Brown, Ben R.,Stuart, Ian A.,Tyrrell, A. William R.
, p. 2563 - 2572 (2007/10/02)
Flav-2-enes have been utilised via 2,3-cis-2-acetoxy-3-bromoflavans for the synthesis of C-2-O-C-3- and C-2-O-C-4-linked biflavonoids.For example, 2,3-cis-2-acetoxy-3-bromoflavans react with (+/-)-tetra-O-methylcatechin (18) to give
Epimerisation of 4-Acetoxyflavans and Flavan-4-ols
Attwood, Michael R.,Brown, Ben R.,Pike, William T.
, p. 2229 - 2236 (2007/10/02)
5,7,3',4'-Tetramethoxyflavan-4β-ol reacts at 0 deg C with pyridine, ang a trace of acetic acid to give the 4β-acetoxy derivative but at 90 deg C the 4α-acetoxyflavan is formed.Either acetate when equilibrated with this acetylating agent yields a mixture o
Synthesis and Reactions of 4-Aryloxyflavans
Bateman, Graham,Brown, Ben R.,Campbell, John B.,Cotton, Charles A.,Johnson, Philip,et al.
, p. 2903 - 2912 (2007/10/02)
4α-Aryloxyflavans unsubstituted in ring A have been synthesised by the reaction of phenols with flavan-4β-ols in the presence of boron trifluoride in ether.If reaction times are prolonged beyond disappearance of the starting 4β-ols, thermodynamic control leads to 4-arylflavans and the yields of 4-aryloxyflavans are negligible. 4-Arylflavans are the sole products when the catalyst is toluene-p-sulphonic acid.Thermal decomposition of flavan-4-yl phenol carbonate in the presence of phenols affords a synthesis of 4α-aryloxyflavans free from 4-arylflavans.Syntheses of 7-methoxy-4α-aryloxyflavans have not been successful, nor can 4-aryloxyflavan-3-ols be obtained from 3,4-diols by these methods.The 4-aryloxyflavans react rapidly with acids to yield 4-carbocations which can be trapped by a variety of nucleophiles yielding 4α-ols with water, 4α-alkoxyflavans with alcohols, 4α-arylflavans with phenols, and 4α-sulphides with thiols. 2,3-cis-Flav-3-ene epoxide reacts with phenols to give 2,3-cis-3,4-cis-4-aryloxyflavan-3-ols and with sodium salts of phenols to give 2,3-cis-3,4-trans-4-aryloxyflavan-3-ols.The 2,3-trans-epoxide similarly gives the 2,3-trans-4-aryloxyflavan-3-ols.A biflavonoid containing a 4-aryloxy link has been synthesised from the 2,3-trans-epoxide and 7-hydroxyflavan-4-one.A series of 2,3-trans-4'-methoxy-4-aryloxyflavan-3-ols has been synthesised from crude 2,3-trans-4'-methoxyflav-3-ene epoxide.The substitution of a methoxy group into position 7 of the flavonoid A-ring prevented the preparation of the epoxides, but the action of N-bromosuccinimide and sodium acetate in acetic anhydride and acetic acid on 7,4'-dimethoxyflav-3-ene gave 2,3-cis- and 2,3-trans-4-acetoxy-3-bromo-7,4'-dimethoxyflavans, the latter of which was converted by the action of sodium salts of phenols into the expected 4-aryloxyflavan-3-ols. 5,7,3',4'-Tetramethoxyflav-3-ene gave nuclear brominated products even with N-bromosuccinimide; thus, the synthesis of 5,6,3'4'-tetramethoxy-4-aryloxyflavan-3-ols has not been possible by this method.
