Fig 1.
Two possible routes from dihydroflavonol to anthocyanidin.
2-Flaven-3,4-diol has not been isolated because of its instability under acidic conditions. (2R, 3S, 4S)-cis-Leucoanthocyanidine was confirmed to be the enzymatic product of DFR and to act as a substrate of ANS.
Fig 2.
Two possible routes from dihydroflavonol to anthocyanidin.
Fig 3.
Calculation results for conversion of dihydroflavonol (CP1) to 2-flaven-3,4-diol (CP4-1) via route B in a neutral aqueous environment.
Fig 4.
The effect of 2-hydroxyl group on the A ring: conversion of 5,7-dehydroxydihydroflavonol (CP1’) to 3-oxo-flavan-4-ol (CP3-1’).
Fig 5.
Calculation results for the late stage of the biosynthesis of anthocyanidin in a neutral aqueous environment.