Phosphorus Ylide Based Functionalizations of Tetronic and Tetramic Acids

Abstract

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.

Enantioselective Total Syntheses of Pallambins A–D

“…These results indicated that the A/B ring system of tetracycle 14 is more crowded than that of 19. This result clearly indicated that the diradical rearrangement required alower energy than the cis/trans isomerization at D 13 (14) .The physical data of our synthesized products 5 and 6 are identical to those reported in the literature (see the Supporting Information). Thep hysical data of our synthesized products 3 and 4 are identical to those reported in the literature (see the Supporting Information).…”

“…[14] It is worth noting that the reaction temperature and the reaction time were critical for the high yield. Heating 15 with (triphenylphosphoranylidene)ketene in mxylene at 160 8 8Cl ed to the acylationo ft he a-hydroxy group and the subsequent intramolecular Wittig reaction to afford tetronic ester 22 in 61 %y ield.…”

“…Heating 15 with (triphenylphosphoranylidene)ketene in mxylene at 160 8 8Cl ed to the acylationo ft he a-hydroxy group and the subsequent intramolecular Wittig reaction to afford tetronic ester 22 in 61 %y ield. [14] It is worth noting that the reaction temperature and the reaction time were critical for the high yield. Higher temperatures and longer reaction times resulted in lower yields.C hemo-and stereoselective reduction of the tetronic ester double bond was then pursued.…”

Tandem-, Domino- and One-Pot Reactions Involving Wittig- and Horner-Wadsworth-Emmons Olefination

“…The prospects of multi-step, one-pot reactions and reaction cascades incorporating Wittig reagents can be seen in the rich chemistry of ketenylidenetriphenylphosphorane (178) (Scheme 45) [182][183][184][185], which has been reviewed earlier [182,186,187]. Lastly, catalytic Wittig reactions can be seen as a subset of tandem reactions involving phosphoranes.…”

Synthesis and Antifungal Activity of Novel Furan‐2,4‐dione Derivatives Containing Substituted Phenylhydrazine Moiety

“…Natural tetronic acid derivatives with a heterocyclic core of furan-2,4(3H,5H)-dione have antioxidant, 1,2 antiviral, 3,4 antibacterial, 5 and antifungal effects, 6,7 which has attracted the interests of chemists. Many different tetronic acid derivatives have been designed and synthesized, and many of the compounds showed noticeable bioactivity especially when a proper substituent such as an aryl, 8 acyl, 9 and alkyl, 10 (compounds a, b and c, Figure 1) were introduced at the 3-position of furan-2,4-dione.…”