Asymmetric total synthesis of rhinacanthin A

First consecutive linear synthesis of hostmaniene, 5-formyl-2-(isopropyl- 1 ’- ol)benzofuran and anadendroic acid using prenylated phenol

“…8 Consecutively, for the syntheses of 10, the crude product 9 was subjected to base-promoted [5-exo-tet]-cyclization reaction by employing LiOH as a base to furnish the racemic benzofuran (10) in 63% yield. 9 However, it was reported that the cyclization of 9 under acidic condition using p-TSA produced a benzohydropyran ring as a major product through [6-endo-tet]-cyclization. Similar observations were also reported by others.…”

Concise Synthesis of (±)-Rhinacanthin A, Dehydro α-Lapachone, and β-Lapachone, and Pyranonaphthoquinone Derivatives

“…20 Due to this importance of pyranonaphthoquinones, synthesis of (±)-rhinacanthin A (3) was first attempted using dehydro-α-lapachone (1). Although the total synthesis of rhinacanthin A (3), as both racemic and enantioenriched products, was respectively achieved in 7 and 8 steps, 21 simple and more concise synthetic approaches are still required. Reaction of 1 with dimethyldioxirane in acetone afforded epoxide 9 in 87%, which was then reduced with NaBH3CN in the presence of BF3·OEt in THF to give (±)-3 in 72% yield with chemo-and regioselectivity (Scheme 2).…”

“…22 The spectral data of synthetic material 3 were in good agreement with those reported in the literature. 21 In view of the great importance of β-lapachone (5), a number of synthetic methods have been reported. 23 The best method for the preparation of 5 is the sulfuric acid-catalyzed cyclization of lapachol.…”

Unusual <i>O</i>-Alkylation of 2-Hydroxy-1,4-naphthoquinone Utilizing Alkoxymethyl Chlorides

“…[1][2][3][4][5][6][7] Recently, our research interests have focused on the total synthesis of naturally occurring naphthoquinones, such as rinacanthin A, 8) dehydroiso-β-lapachone 9) and lantalucratins 10) having biological activities including anti-tumor activity, in order to confirm the chemical structure and determine the absolute configuration. In the course of our synthetic study, a key intermediate (I) was prepared from 1,4-dimethoxynaphthalene, which is relatively expensive as a commercial source, by the introduction of a hydroxyl group using directed ortho lithiation-substitution reaction 11) and the following hydroxyl protection by methoxymethyl group (Chart 1).…”