- (±)-Diinsininone: made nature's way
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We report the synthesis of diinsininone (33), the aglycone of (±)-diinsinin (2). Thereby, we complete the first construction of a proanthocyanidin (PA) type-A compound incorporating a [3.3.1]-bicyclic ketal as its characteristic core. Our strategy utilizes a coupling between a benzopyrilium salt and a flavanone that proves applicable to other PA type-A compounds. During this undertaking, treatment of naringenin (9) with 2-iodoxybenzoic acid (IBX) followed by reductive work-up affords eriodictyol (10). This reactivity mirrors that of catechol hydroxylase (F3H) found in the flavonoid pathway. Other interesting transformations include the formation of flavonoids through an ortho-quinone methide (o-QM) cycloaddition-oxidation sequence and regioselective β-glycosidations of several unprotected flavanones suggesting a likely synthesis of 2 from the aglycone 33.
- Selenski, Carolyn,Pettus, Thomas R.R.
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p. 5298 - 5307
(2007/10/03)
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- Total synthesis of apigenin 7,4′-di-O-β-glucopyranoside, a component of blue flower pigment of Salvia patens, and seven chiral analogues
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We have succeeded in the first total synthesis of apigenin 7,4′-di-O-β-D-glucopyranoside (1a), a component of blue pigment, protodelphin, from naringenin (2). Glycosylation of 2 according to Koenigs-Knorr reaction provided a monoglucoside 4a in 80% yield, and this was followed by DDQ oxidation to give apigenin 7-O-glucoside (12a). Further glycosylation of 4′-OH of 12a with 2,3,4,6-tetra-O-acetyl-α-D- glucopyranosyl fluoride (5a) was achieved using a Lewis acid-and-base promotion system (BF3·Et2O, 2,6-di-tert-butyl-4- methylpyridine, and 1,1,3,3-tetramethylguanidine) in 70% yield, and subsequent deprotection produced 1a. Synthesis of three other chiral isomers of 1a, with replacement of D-glucose at 7 and/or 4′-OH by L-glucose (1b-d), and four chiral isomers of apigenin 7-O-β-glucosides (6a,b) and 4′-O-β- glucosides (7a,b) also proved possible.
- Oyama, Kin-Ichi,Kondo, Tadao
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p. 2025 - 2034
(2007/10/03)
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- Chiral molecular recognition on formation of a metalloanthocyanin: A supramolecular metal complex pigment from blue flowers of salvia patens
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Most blue flower color is the result of a metalloanthocyanin, a stoichiometric self-assembled supramolecular pigment consisting of six molecules of an anthocyanin, six molecules of an anthocyanin, six molecules of flavone, and two metal atoms. We have iso
- Kondo, Tadao,Oyama, Kin-Ichi,Yoshida, Kumi
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p. 894 - 897
(2007/10/03)
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