Novel Cinnamoylated Flavoalkaloids Identified in Tea with Acetylcholinesterase Inhibition Effect

3-O-Cinnamoylepicatechin (1) was synthesized along with four flavoalkaloids, (−)-6-(5‴S)-N-ethyl-2-pyrrolidinone-3-O-cinnamoylepicatechin (2), (−)-6-(5‴R)-N-ethyl-2-pyrrolidinone-3-O-cinnamoylepicatechin (3), (−)-8-(5‴S)-N-ethyl-2-pyrrolidinone-3-O-cinnamoylepicatechin (4), and (−)-8-(5‴R)-N-ethyl-2-pyrrolidinone-3-O-cinnamoylepicatechin (5) via esterification of epicatechin followed by phenolic Mannich reaction of 1 with theanine in the...