Bislactones synthesis

As in the synthesis of (+)-26 (Scheme 8), treatment of (-)-27 with chromic acid accomplishes oxidative scission of the carbon-carbon double bond, and provides (-)-26 after an intramolecular bislactonization reaction (Scheme 16). By analogy to the conversion of 50 into 51 (see Scheme 8), treatment of (-)-26 with ammo-... 

Preparation of bioactive podolactones via a new Pd-catalysed bislactonization reaction. Synthesis of oidiolactone C. Barrero, A. F. Quflez del Moral, J. F. Cuerva, J. M. Cabrera, E. Jimenez-Gonzalez, D. Tetrahedron Lett. 2000, 41, 5203-5206. 

These furanes can be used for synthesis of bislactones or y-hydroxybutenolides by reaction with aldehydes or ketones in the presence of TiCl4 (equations II and III). 

FuranonesS The first step in a simplified synthesis of bislactones involves condensation of an a-halo aldehyde (1) and potassium ethyl malonate (2) in benzene- water in the presence of tetra-n-butylammonium bromide. The furanone 3 is converted to the hislactone 4 by bromination followed by treatment with HBr. The product is a precursor to df-avcnaciolide (5), a fungicide from Aspergillus arenaceous. 

Synthesis of crown ether bislactones using caesium carboxylates of pyridine and of benzene dicarboxylic acids, O. Piepers and R. M. Kellog, J. Chem. Soc., Chem. Commun., 1978, 383. 

C2-symmetric teraryls. The synthesis was accomplished by palladium-catalysed intramolecular coupling, with subsequent ester saponification, methyl ether cleavage and two-fold ring closure to give the expected bislactone (Scheme 5.52). ... 

It should finally be mentioned that the nucleophilic group in Pd-catalyzed tandem reactions based on oxycarbonylation can also be a carboxyl function. " Some convincing examples were reported by Yoshida, Tamaru, and co-workers who used this reaction for the stereoselective synthesis of bislactones (Table 6). Following the mechanistic pattern shown in Scheme 14 the carboxyl group at first attacks the alkene. The intermediate Pd-acyl species then reacts with the hydroxy function to give a m-fused bislactone. A substituent in 2-position increases the reactivity however, substituents at the double bond have no significant influence on the reaction. 

The bislactonization procedure adapted by Corey from the earlier work of Alder for the synthesis of picrotoxinin (4, 79) has been shown to be applicable to several simple substrates e.g. (69) -> (70). The rra 5-isomer of (69) gives largely the ( )-isomer of (70) under suitable conditions. 

Thus, in the synthesis of bislactone lignans such as 335 the aldol addition to succinic anhydrides has been employed [108]. Anhydride 331 is deprotonated and treated with aldehyde 333. The primary adducts 334 and 336 spontaneously open the anhydride ring and rearrange to the lactones 335 and 337. The on-ring stereogenic center is controlled by the adjacent side chain. A crucial diastereo differentiation... 

An imino-Claisen rearrangement allows access to lactone 51 (as a 1 1 mixture of epimers) which, following isomer separation, was converted to (-i-)-canadensolide 52, (-)-santolinolide A 53 and (+)-santolinolidc B 54 (Scheme 9). Lee et al have described the synthesis of additional rigid bicyclic analogues of diacylglycerol (see Vol. 26, p.307). Bislactones 55 and 56 were obtained from L-arabinose and the positional isomers 57 and 58... 

Avenaciolide is a novel fungicidal bislactone first isolated from cultures of Aspergillus avenaceus G. Smith. The synthesis of avenaciolide, outlined below, is based on a new method for synthesis of a-methylene-y-butyrolactones developed at the Dow Chemical Company. ... 

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