Total Synthesis of Cristatic Acid

Abstract

The first total synthesis of cristatic acid 1, an antibiotic endowed with considerable activity against Gram-positive bacteria, hemolytic properties, and significant cytotoxicity, is described. Key to success are the formation of its 2,4-disubstituted furan moiety via a palladium-catalyzed alkylation of vinylepoxide 10 derived from sulfonium salt 8 and the use of SEM ethers as the protecting groups for the phenolic OH functions

Meroterpenoid Pigments from Albatrellus flettii (Basidiomycetes)

“…[2] On stirring a 2:1 mixture of 7 and 8 in dichloromethane at room temperature, the solution gradually turned blue and, after two weeks, albatrellin could be isolated in 30 % yield. Since each of the starting materials, grifolin (1) [8] and cristatic acid (3), [9] have already been prepared by total syntheses, this constitutes a formal total synthesis of albatrellin.…”

“…Similarly, the reaction of quinone 7 with cristatic acid (3) yielded 32 % of 4Ј-carboxyalbatrellin (9). The latter is rather unstable and suffers easy decarboxylation to albatrellin (4) even on standing in the refrigerator.…”

Total synthesis of radulanin H and proposed structure of radulanin E

“…Regioselective C-allylation of 5 was next attempted (Scheme 3). We initially examined the reaction according to Fü rstner's procedure, 9 in which the C-allylation of resorcinols proceeded regioselectively. When 5 was treated with allyl bromide and NaH in toluene at 80 C, the desired C-3 allylated product 8 was produced in 38% yield (Table 1, entry 1).…”

Vinylepoxides in Organic Synthesis

“…When an aliphatic aldehyde is allowed to react with a semistabilized or nonstabilized sulfur ylide, poor diastereoselectivities and yields are observed, due to problems in controlling the ylide conformation and competing ylide rearrangement reactions [71]. However, some racemic, aliphatic vinylepoxides have been successfully formed by sulfur ylide epoxidations, although varying diastereoselectivities were observed [78][79][80]. [81].…”