Naturally occurring compounds related to phenalenone. II. Synthesis of hemocorin aglycon.

Abstract

2,7-Dibromo-3,6-dimethoxynaphthalene reacted with BuLi, Me borate, H2O, and H2O2 to give 3,6-dimethoxy-2,7-naphthalenediol, which was methylated to 2,3,6,7-tetramethoxynaphthalene. Vilsmeier formylation then gave 2,3,6,7-tetramethoxy-1-naphthaldehyde, which was condensed with Ph3P:CHCO2Et and hydrolyzed to give the 2,3,6,7-tetramethoxy-1-naphthaleneacrylic acid (I). I was hydrogenated and cyclized with polyphosphoric acid to 2,3-dihydro-4,5,8,9-tetramethoxyphenalen-1-one. Reaction with PhMgBr gave a stable carbinol, which was dehydrated (HCl) to 4,5,8,9-tetramethoxy-3-phenylphenalene. Dehydrogenation with 2,3-dichloro-5,6-dicyano-p-benzoquinone then gave a mixt. of the di-Me ethers A (II) and B (III) of hemocorin aglycon. 2,3-Dihydro-4,9-dimethoxyphenalen-1-one (IV) was similarly prepd. from 2,7-dimethoxy-1-naphthaldehyde. SeO2 oxidn. of IV gave 9-hydroxy-4-methoxyphenalen-1-one, also obtained when IV was treated successively with p-nitrosodimethylaniline and HCl-EtOH. Oxygenation of IV in Me3COH-KOCMe3 gave 2-hydroxy-4,9-dimethoxyphenalen-1-one. [on SciFinder(R)]