3- Alkoxyacrylic esters

In contrast with olefins, alkoxy-alkoxycarbonylation of alkynes to give /3-alkoxyacrylic esters is not a common reaction, and has occasionally been observed as a side reaction of the main reaction pathway leading to maleates and fumarates [77,80]. However, with suitably functionalized alkynes bearing a coordinating group (such as a,a-disubstituted propargylic acetates) it may become the major reaction course (Scheme 15) [88]. 

Not merely alkoxymethylene derivatives from compounds containing reactive methylene groups, but also other enol ethers can be cleaved by amines, e.g., 3-alkoxyacrylic esters,1096 4-pyrones,1097,1098 and furfuraldehyde.1099... 

Vinyl esters are silylated at the trigonal a-carbon, making available the enol esters of silyl ketones. The regioselective deprotonation of )3-alkoxyacrylic esters and the ability of the lithio derivative to undergo a tandem Michael-Julia condensation with suitable acceptors are exploitable in the synthesis of highly functionalized cyclopentenones. ... 

Addition to conjugated alkynoate esters. The addition of alcohols to the esters to give enol derivatives is catalyzed by AgOTf. While this reaction is suitable for the preparation of 3-alkoxyacrylic esters and 2-alkoxyfumaric esters, unsymmetrical alkynoic esters afford mixtures of products. 

Macralstonine, C44H54N4O5, crystallizes as colorless, rectangular rods, mp 293° (dec.), [a]D +27.5°, and contains one methoxyl, at least two C-methyl, and three, or possibly four, methylimino groups (33, 36). Its IR-spectrum discloses the presence of an imino or hydroxyl group, an alkoxyacrylic ester chromophore (peaks at 1652 and 1628 cm-1), and an o-disubstituted benzene nucleus. The formation of a derivative with dinitrophenylhydrazine indicates the presence of a potential carbonyl function. Macralstonine has also been reported to possess a marked hypotensive activity (36). 

Spectral data readily demonstrated the presence of indole, methyl /8-alkoxyacrylate, and hexoside functions. Ions in the mass spectrum of the acetate at m/e 183,182,169, and 168 (rather than the more common series m/e 184, 183, 170, and 169) indicated a tetrahydro-/3-carboline with a substituent a to N-4 however, the most distinctive feature was the ready loss of CO and C02 from the molecular ion which was attributed to the breakdown of a lactone. Accordingly, treatment with sodium methoxide opened the lactone ring, and reactylation gave a methyl ester pentaacetate... 

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