Pulvinic acids and pulvinones

In studies of later stages in the biosynthesis of the chromanated pulvinone (69) from the 4,4 -dihydroxy pulvinone (64) in A, terreus, Seto and co-workers (78, 79) have been able to separate a cell-free enzyme system from the fungus which catalyses the transfer of the prenyl-moiety from 3,3-dimethylallyl pyrophosphate to the aryl rings of 

Although the pulvinic acid amide derivatives rhizocarpic acid and epanorin (58) could originate from simple coupling between the appropriate amino acid and the pulvinic acid, Maass (66) has proposed a direct route to pulvinamide itself (viz 58, R = H), involving condensation between phenylalanine and phenylpyruvic acid. 

In 1985, Campbell et al. [58] employed a Dieckmann condensation strategy to the synthesis of pulvinones. By this route, Campbell prepared tetronic acid 61 that can be either transformed to phosphorane 62 and utilized in Wittig reactions or condensed with arylaldehydes that can afford pulvinones after dehydration. The first route led Steglich s group in 2000 to the total synthesis of aurantricholides A (65) and B (66), two minor pigments of toadstool Tricholoma aurantium [59], whereas 

Furthermore, the Dieckmann condensation strategy has also been employed in the synthesis of pulvinic acids [61]. Interestingly, 30 years after the first relevant report by Weinstock et al. [61a], the group of Le Gall [61b] presented a versatile route for that purpose. Le Gall improved the synthesis of tetronic acid 61, previously prepared by Campbell et al. [58], by devising a tandem transesterification/Dieckmann 

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Several hydroxylated diarylcyclopentenones closely related to the pulvinic acids and pulvinones are found in some species of Boletales (Table 13). Their presence indicates the close relationship of Gyrodon to Gyroporus and the Paxillaceae and is strong evidence for inclusion of the gastroid Chamonixia in Boletales. 

Alternatively, the pulvinone nucleus of pigment (115) could derive via oxidative decarboxylation of the hypothetical intermediate (9) already implicated in the biosynthesis of grevillins, terphenylquinones (and hence pulvinic acids), and the pigment (10). 

The group of 4-ylidenetetronic acid pigments known as pulvinones are closely related to the pulvinic acids and possess the general structure (60). It is interesting that pulvinones have only very recently been... 

Olefination reactions of the phosphonates (254) and (255) derived from hydantoin and 1-methylhydantoin, respectively, provide good yields of the expected C-5 unsaturated hydantoin derivatives (256), generally as mixtures of isomers. 52 Heterocyclic analogues, e.g. (257), of pulvinones and, e.g. (258), of permethylated pulvinic acids have been synthesized by Wadsworth-Emmons reactions of the phosphonates (259) and (260), themselves prepared directly from substituted maleic anhydrides. 55 The reaction of ylide (261) with aldehydes to give (262) has been used as a key... 

Patenden et al. [46] synthesized heterocyclic analogues of pulvinones 52-55 and of permethylated pulvinic acids 56, 57 which were found in higher fungi (Scheme 21). All compounds possessing lactonic structures were synthesized in the Horner-Wittig reaction using the corresponding heteroaryl aldehydes and 4-dimethoxy-phosphorylated lactone 58. The latter was obtained as the main product in the reaction between substituted maleic anhydrides 59 and sodium dimethyl phosphite via the postulated carbene. 

In 1975, Pattenden etal. reported the first regiospecific synthesis of permethylated pulvinic acids 46 [48] and pulvinones 45 [49] by condensation of 44 with aroyl formates and aryl aldehydes, respectively, followed by dehydration (Scheme 1.5). Interestingly, Pattenden s pioneering work allowed the first total synthesis of naturally occurring pulvinones, first isolated from natural sources in 1973 [3b] but... 

Syntheses, published in 1976, of naturally occurring tetronic acids include those of (S )-carlosic acid (75) and the related (/ )-carolic acid and of fungal pigments based on the pulvinone e.g. 76) and pulvinic acid e.g. 77) structures. 

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