How to Increase the Reactivity of Hydroxylmethylation of Tea Catechins?
-A Theoretical Study of the Introduction of a Galloyl Moiety at C-3 Position-

Katsuhiro TAMURA^a, Takatoshi MATSUMOTO^b and Umpei NAGASHIMA^b,c*

(Received: July 17, 2000; Accepted for publication: September 5, 2000; Published on Web: November 10, 2000)

Tea catechins and related compounds, (-)-Epicatechin gallate and (-)-Epigallocatechin gallate, which have a galloyl moiety at the C-3 position (see Figure 1), show higher reactivity of hydroxylmethylation than others. We performed theoretical calculations on 5 tea catechins by the semi-empirical molecular orbital method.
It is found that introduction of a galloyl moiety makes HOMO localize at the C-6 and C-8 positions. These variations of orbital energies lead to a high reactivity. It is suggested that the introduction of functional groups that have a large -electron system into tea catechins raises the reactivity of hydroxylmethylation.

Keywords: (+)-Catechin, (-)-Epicatechin, (-)-Epigallocatechin, (-)-Epicatechin gallate, (-)-Epigallocatechin gallate, Hydroxylmethylation, HOMO-LUMO energy

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