Total synthesis of microcarpalide

Synthetic Studies of Natural 10-Membered Lactones, Mueggelone, Microcarpalide, and Sch 642305, Which Have Interesting Bioactivities

“…28,29) Olefinic alcohol 21 was synthesized by Sharpless asymmetric dihydroxylation (AD) 30,31) of unsaturated ester 20 and the following introduction of a C 2 unit. On the other hand, acid 23 was derived from the known compound 22, 32,33) which was easily obtained from D-mannose.…”

“…RCM of tribenzyl ether 32 (high dilution, 0.52 mM) with 1st-generation Grubbs 26) catalyst resulted in exclusive formation of E-isomer 33, but with poor conversion (43%). Finally, deprotection was performed using TiCl 4 , under similar conditions as Gurjar's, 28) to afford microcarpalide. The total yield was not sufficient in their synthesis, but employing Matteson's asymmetric homologation for construction of all stereochemistry appeared to be a steady and unique approach.…”

Métodos de preparação de lactonas de anel médio

“…Esta estratégia também foi utilizada por diferentes grupos na síntese total do microcarpalídeo [74][75][76][77][78][79] . Assim, o grupo de Carda e Marco 74 efetuou a reação de metátese olefínica, obtendo uma mistura das lactonas E e Z, na proporção de 2:1, respectivamente, da qual a lactona (E) pôde ser isolada por coluna cromatográfica.…”

“…Gurjar et al 76 obtiveram o microcarpalídeo por uma reação de metátese seguida de desproteção das hidroxilas (Esquema 34).…”

TiCl4, Dioxane—A Facile and Efficient System for De-O-Benzylation, De-O-Allylation, and De-O-Xylylation of Phenolic Ethers

“…[14] Lewis acids such as BCl 3 , [15] BBr 3 , [16] AlCl 3 [17] are also known to act as reagents for de-O-benzylation. Recently Gurjar et al [18] has used TiCl 4 for de-O-benzylation in the total synthesis of microcarpalide. De-O-allylation has been reported by Chen et al [19] using tetra butyl ammonium peroxy disulphate.…”