Studies on Naturalp-Terphenyls: Total Syntheses of Vialinin A and Terrestrin B

Total Synthesis of Thelephantin O, Vialinin A/Terrestrin A, and Terrestrins B–D

“…Vialinin A/terrestrin A ( 4 ) and terrestrin B ( 5 ) were first synthesized by Takahashi et al , The synthetic path was followed later by Fujiwara to prepare a reference compound for identification of 4 isolated from T. aurantiotincta . Because the path included some technical and poorly reproducible steps due to the oxidation-sensitive middle ring of the p -terphenyl skeleton, the steps were modified to obtain a reasonable amount of 4 .…”

“…Our synthesis of 2′,3′-diacyloxy- p -terphenyl compounds 1 – 5 , outlined in Scheme , employed an isopropylidene acetal group, instead of the methylene acetal group in the previous synthesis, , for protection of the 1,2-diol of the central benzene ring, with the aim of simultaneously removing it and the TBS ethers of the terminal benzene rings under acidic conditions at the final stage. The installation of unsymmetrical or symmetrical diester was scheduled after the construction of the p -terphenyl skeleton by Suzuki-Miyaura coupling of triarylboroxine 7 and dibromide 8 , derived concisely from commercially available benzene-1,2,4-triol ( 9 ).…”

“…The p -terphenyl skeleton was constructed from 8 by Suzuki–Miyaura cross-coupling under standard conditions (Scheme ). The reaction of 8 with 7 in the presence of (Ph 3 P) 4 Pd and K 2 CO 3 in refluxing aqueous 1,4-dioxane successfully afforded p -terphenyl 6 (92%), of which the MOM groups were oxidatively removed with DDQ in the presence of TsOH·H 2 O, according to the Takahashi procedure, , to give o -quinone 14 (98%).…”

“…Symmetrical diesters 20 and 21 were synthesized via diesterification of the dianion of 15 , in line with Takahashi’s method, in good yield (81% and 98%, respectively, over two steps).…”

Recent Applications of Phosphane-based Palladium Catalysts in Suzuki-Miyaura Reactions Involved in Total Syntheses of Natural Products

“…Treatment of C26 with 2,3-dichloro-5,6dicyanobenzoquinone (DDQ) in the presence of p-TsOH in benzene at 50°C provided o-quinone 109, which by reduction with Na2S2O4 gave the corresponding catechol 110 (Scheme 26). Compound 111, which was obtained by acylation of 110, underwent reaction with 2.5 equiv of Pb(OAc)4 in benzene at 80 °C to provide 112 in a high yield.Finally, exposure of 112 to mild acidic conditions gave vialinin A (31) (Scheme 26) [107].…”