Polystyrene-bound cumulated ylide Ph3PCCO was prepared on a large scale in two steps. It reacts with Grignard compounds, amines and alcohols to give immobilized acyl, amide and ester ylides, respectively. Their Wittig reactions lead to alkenes free of phosphane oxide. Optically pure 5-substituted tetramates were obtained from reactions of resin-bound Ph3PCCO with alpha-ammonium esters in one step. The mycotoxin (-)-tenuazonic acid was accordingly prepared in just three steps.

The versatility of the ylide (triphenylphosphoranylidene)ketene (Ph 3 P=C=C=O, 3) in the construction of tetronic and tetramic acids from various carboxylic acid derivatives is demonstrated by new reactions and extensions of known ones. With a-hydroxy or a-amino esters, 3 affords tetronates or tetramates. A twostep synthesis of (-)-epi-blastmycinolactol shows that allyl a-hydroxy esters can be domino Wittig-Claisen reacted to give 3-allyltetronic acids. More extended Wittig-Claisen-Conia cascades can produce 3-alkylidenefuran-2,4-diones, the photooxygenation of which furnishes lactone endoperoxides with antiplasmodial potential. Tetronic acids can be acylated by 3 at C3 to give the corresponding acyl ylides. Their saponification yields the respective 3acetyl compounds, e.g. the fungal metabolite pesthetoxin. a-Hydroxy acids react with 3 to afford the corresponding 3-phosphoranylidenefuran-2,4-diones. The antibiotic (R)-reutericyclin was built up from benzyl D-leucinate and 3 in four steps by downstream acylation first at C3, then at N1 without racemization.

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Pyrrole derivatives R 0120Domino Conversions of Allyl Tetronates and 4-Allyloxycoumarins to all-trans 1,3,4,5-Tetrasubstituted γ-Butyrolactams. -A regio-and stereoselective one-pot synthesis of the title compounds proceeds via spirocyclopropanes of type (XVI), which undergo ring-opening in the presence of amines with R > -Et. In the case of (IIIc) andV), 10% of 3,4-cis-isomers are additionally obtained; however, their structures are not further specified. Reaction of diastereopure (XVI) with the soft nucleophile cyclohexene under ZnCl2 catalysis furnishes (XVIII) as the sole product of a formal [5+1] cycloaddition. -(SCHOBERT*, R.; BIESER, A.; MULLEN, G.; GORDON, G.; Tetrahedron Lett. 46 (2005) 33, 5459-5462; Lab. Org. Chem., Univ. Bayreuth, D-95440 Bayreuth, Germany; Eng.) -R. Steudel 48-131