Feringa-butenolide

Feringa-butenolide 114, in the presence of Dess-Martin periodinane reagent and 2,6-lutidine, gave the bis-ketone 115 which underwent intramolecular cycloaddition to afford endo-selectively the desired decalin-based lactone 116 (Equation 2.32) [114]. Double activation of butenolidic double bond strongly increases the reactivity of dienophile 115. 

Jauch achieved the short and elegant total synthesis of mniopetals during almost the same period in which our total syntheses were reported [36-41]. We briefly introduce Jauch s achievements on this subject. The key step of his synthesis was the IMDA reaction of 2-substituted butenolide 124 (Scheme 20), which was prepared by the diastereoselective PhSeLi-induced Baylis-Hillman reaction of 122 and Feringa s butenolide 123 [99]. The cycloadduct of this IMDA reaction 125 was transformed into kuehneromycin A and mniopetals E and F, respectively. 

The synthetic utility of (5S)- and (5R)-menthyloxy-2(5H)-furanones has been extensively explored and is well documented. The ready availability of these enantiomerically pure butenolides via the singlet photooxygenation of furfuraF and their wide range of reactivity contribute to their popularity as chiral building blocks. The present procedure for the preparation of the title compound and the useful epimerization step are modifications of methods originally reported by Feringa and co-workers. ... 

Thus, having identified an intramolecular Diels-Alder reaction between a diene and a connected butenolide as the key step for the construction of the aforementioned target, a new variant of the BayHs-Hillman reaction was performed, with the aim of tethering the required chiral Feringa s butenolide (592) to the Wang resin immobilized diene-aldehyde (591) using PhSeli as the nucleophile (Scheme 123). 

Recently, Feringa explored also another variant of this methodology by replacing (5/ )-menthyloxyfuran-2(5//)-one with another chiral butenolide, namely (/ )-5-acetoxyfuran-2(577)-one (113), Scheme (20) [76,77]. The chiral butenolide was obtained in several gram scale by enzymatic esterification of 5-hydroxyfuran-2(577)-one (111) using lipase R immobilized on hyflo super cell. 

Asym. diene synthesis. Butadiene bubbled into a reactor containing startg. chiral butenolide and a little hydroquinone at — 78°, and the stoppered vessel heated at 210° for 24h (lR,6S,7R)-7-methyl-8-oxabicyclo[4.3.0]non-3-en-9-one. Y 63% (dia-stereoisomerically pure). F.e. and regiospecific conversion of isoprene in the presence of AICI3 s. R.M. Ortuno et al.. Tetrahedron 44,1711-9 (1988) ibid. 45,1833-8 (1989) asym. 1,3-dipolar cycloaddition to 5-menthyloxy-2(5/f)-furanones s. B. de Lange, B.L. Feringa, Tetrahedron Letters 29, 5317-20 (1988). 

Mao B, Geurts K, Fananas-Mastral M, van Zijl AW, Fletcher SP, Minaard AJ, Feringa BL (2011) Catalytic enantioselective synthesis of naturally occurring butenolides via hetero-allylic alkylation and ring closing metathesis. Org Lett 13 948-951... 

B. Mao, Y. Ji, M. Fananas-Mastral, G. CaroH, A. Meetsma, B.L. Feringa, Highly enantioselective synthesis of 3-Substituted y-butenolides by palladivun-catalyzed kinetic resolution of unsymmetrical allyl acetates, Angew. Chem. Int. Ed. 51 (2012) 3168-3173. 

A remarkable kinetic resolution was observed recently by Feringa and coworkers when 2-silyloxyfuran was reacted with the racemic unsymmetrical allylic substrate 86, catalyzed by the palladium complex of Trost s ligand (/ ,/ )-14, as illustrated in Scheme 5.28. The acetate anion liberated upon oxidative addition of palladium(O) is assumed to cleave the silyl protecting group, so that the enolate anion forms aside from TMSOAc. After allylic alkylation of that enolate, double bond migration leads to butenolide (R)-87 isolated in 47%, if the reaction was run with 52% conversion. Not only the product 87 but also the recovered acetate... 

---