Echimidinic acid

Dibsters of Nbcine and Two Different Monocarboxylic Acids a. Echimidine (retronecine and angelic, echimidinic acids). 

The conclusion was reached that the biosynthetic route was by way of a two-carbon insertion into 2-oxo-3-hydroxy-3-methylbutyric acid (CLXXIV). Taken in conjunction with the established bios3uithesis of valine (CLXXV) from pyruvic acid by way of acetyllactic acid (CLXXVI) and the ketol rearrangement to CLXXIV the biosynthesis of echimidinic acid may be formulated as in Chart VI. 

T. incanum and echimidinic acid in helibsupine in C. officinale, two plants of the same tribe (Cynoglosseae) of the family Boraginaceae, suggested to... 

In summary it is to be noted that the evidence available now on the biosynthesis of the necic acids points to branched-chain amino-acids as precursors. As discussed in part above, isoleucine has been shown to be a precursor for the necic acids of the senecic [as (47)] and monocrotalic (49) types, and of the angelic acid component of heliosupine. " Valine, on the other hand, is a specific precursor of the echimidinic acid (51) moiety in heliosupine. 

Fig. 198. Formation of pantoic and echimidinic acids 1 Ketopantoate hydroxymethyltransferase 2 ketopantoate oxidoreductase...

In 1966, labelled L-threonine and L-isoleucine were observed to be incorporated into the seneciphyllic acid [63]. Similarly, it was described that labelled DL-valine is a precursor of echimidinic acid [64]. The five-membered angeloylic acid is... 

Crout DHG (1966) Pyrrolizidine alkaloids. The biosynthesis of echimidinic acid. J Chem Soc (C) 21 1968-1972... 

Various carboxylic acids are found as the necic acid parts of the pyrrolizidine alkaloids, e.g. senecionine 6.77), monocrotaline 6.78) and heliosupine 6.79). Available evidence [61, 62] points to the derivation of these acids from the branched-chain amino acids isoleucine and valine (see dotted lines). [In the case of monocrotaline C-4, C-5, and C-8 apparently derive from propionic acid. Carbon atoms 5 and 6 of the echimidinic acid fragment in 6.79) apparently derive from acetate.] The basic fragment in these alkaloids, retronecine 6.80), is formed [63] from two molecules of... 

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