Nephromopsinic acid

A heterocoupling reaction has been applied in the course of the synthesis of (+)-nephromopsinic acid [95] and for the preparation of 3-alkylsubstituted indoles [96],... 

Mulzer J, Kattner L, Strecker AR, Schroder C, Buschmann J, Lehmann C, Luger P (1991) Highly Felkin-Anh selective Hiyama additions of chiral allylic bromides to aldehydes. Application to the first synthesis of nephromopsinic acid and its enantiomer. J Am Chem Soc 113 4218-4229... 

The fatty acids of lichens show some resemblance to those in non-lichen-forming fungi, but none are identical. Aliphatic acids, much rarer in lichens than in other plant groups, appear to be formed in a very different manner through the tricarboxylic acid cycle. Known higher aliphatic acids and related substances are acaranoic acid, acarenoic acid, (+)-aspicilin, (—)-caperatic acid, (—)-lichesterinic acid, linoleic acid, (—)-nephromopsinic acid, (+)-nephrosteranic acid, (+)-nephrosterinic... 

Lichesterylic acid and methyl protolichesterinate have been found in Cetraria islandica (555) the latter ester was prepared from the potassium salt of protolichesterinic acid and methyl iodide 413). Allo-protolichesterinic acid adds diazomethane to form isomeric pyrazoline methylesters, the stereochemistry of which was established by their respective CD spectra. Hydrogenation of allo-protolichesterinic acid with Pd-C in acetic acid produces a mixture of (-)-dihydro-allo-protolichesterinic acid (33), (-)-nephromopsinic acid (34) and (-)-lichesterinic acid (35) (see Scheme 34). 

Mulzer et al. 553) synthesized (-)-nephromopsinic acid by the addition of a chiral allylic bromide to tetradecanal (see Scheme 36). The same group 628, 666) also described total syntheses of (-)- and (+)-roccellaric acid and (-)-dihydroprotolichesterinic acid and secured the relative configuration of (+)-roccellaric acid by an X-ray analysis. One route started from (2S,3E)-l,2-isopropylidene-5-0-benzyl-3-pentene-1,2,5-triol (42) (see Scheme 37). The second route included the ozonisation of methyl-(2RS,3R,4E)-3-benzyloxy-5-hydroxy-oxolan-3-one and subsequent condensation with tridecyltriphenylphosponium bromide (see Scheme 38). Finally they synthesized (-t-)-roccellaric acid and (-l-)-dihydroprotolichesterinic acid from D-glucose as the chiral pool (552) (see Scheme 39). 

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