By a simple process, 3-methoxyjuglone (= 8-hydroxy-2-methoxy-1,4-naphthoquinone; 9) has been synthesized from 1,2,4-trimethoxybenzene (5) and converted, after prenylation, to α-caryopterone (1; Scheme 1), a pyranojuglone pigment from Caryopteris clandonensis. On the other hand, juglone (= 5-hydroxy-1,4-naphthoquinone; 12) was regioselectively prenylated at C(2) via its 1-methoxy-cyclohexa-1,3-diene adduct 15(Scheme 2). The 2-prenyljuglone (4) thus formed led to 1 after oxidation and other reactions.

This study demonstrates a simple process for synthesizing -caryopterone, a pyranojuglone pigment from Caryopteris clandonensis, and demonstrates its potential as a bioluminescent pigment.

Two New Syntheses of the Pyranojuglone Pigment α‐Caryopterone

Key Takeaway: This study demonstrates a simple process for synthesizing -caryopterone, a pyranojuglone pigment from Caryopteris clandonensis, and demonstrates its potential as a bioluminescent pigment.