Naphthopyranquinones. Confirmation of the structures of the ventiloquinones E, G and J by synthesis

Abstract

Both ventiloquinone E (cis-3,4-dihydro-6,7,9-timethoxy-1,3-dimethyl-1H-naphtho[2,3-c]pyran-5,10-quinone)1 and ventiloquinone G (cis-3,4-dihydro-5,7,10-trihydroxy-1,3-dimethyl-1H-naphtho[2,3-c]pyran-6,9-quinone)3 have been synthesised and shown to be identical with natural samples isolated from the root bark of Ventilago maderaspatana. cis-3,4-Dihydro-5-hydroxy-7,10-dimethoxy-1,3-dimethyl-1H-naphtho[2,3-c]pyran-6,9-quinone 5 has also been synthesised and found to be different to ventiloquinone J, which must then be cis-3,4-dihydro-10-hydroxy-5,7-dimethoxy-1,3-dimethyl-lH-naphtho[2,3-c]pyran-6,9-quinone 4.