A new synthesis of racemic coronamic acid and other cyclopropyl amino acids

Diastereoselective Synthesis of Cyclopropane Amino Acids Using Diazo Compounds Generated in Situ

“…Interestingly, the pyrazoline cycloadduct was never detected in this or subsequent thermal reactions. While there is an example in the literature of this pryazoline cycloadduct having been isolated from the addition of phenyldiazomethane to dihydroamino acid 5 , the reaction was conducted at −15 °C, and presumably, the pyrazoline was stable enough to be characterized at room temperature . On heating at 90 °C in toluene, elimination of nitrogen occurred to yield cyclopropane amino acid 9 .…”

“…Finally, the formation of cyclopropane amino acids can be accomplished by the addition of dipoles or ylides to dehydroamino acids (routes IIIb and IIIc). While the Michael addition of sulfur ylides to dehydroamino acids leads directly to cyclopropane amino acids (route IIIb), ,, the 1,3-dipolar cycloaddition of diazo compounds onto dehydroamino acids furnishes the desired cyclopropane after extrusion of nitrogen from the pyrazoline intermediate (route IIIc). , …”

Synthetic Approaches to Coronafacic Acid, Coronamic Acid, and Coronatine

“…61 Stammer and co-workers developed a synthesis of (±)-5 that featured the addition of a diazonium species to a dehydroalanine derivative (Scheme 32). 78…”

Olefinic microbial metabolites, excluding macrocyclic compounds

“…84 The 1,3-dipolar cycloaddition of diazoalkanes to a protected 2-aminoacrylic acid, followed by thermolysis of the pyrazoline that is thus formed, is the basis of a simple new synthesis of the cyclopropyl amino acid coronamic acid, which is found as an amide in coronatine (101) (a phytotoxic metabolite of Pseudomonas coronafaciens). 86 An esterified amino-acid unit features in the structures that have been reported for the AK-toxins I (102a) and I1 (102b) on the basis of spectroscopic data;87 the AK-toxins are host-specific phytotoxic metabolites of Alternaria kikuchiana, which is the causal fungus of black spot disease on susceptible cultivars of Japanese pear (Pyrus serotina var. culta).…”

“…66 The racemic 'right-wing' tetrahydroindane-lactone (83), which is available as reported previously by these authors (using an intramolecular Diels-Alder cycloaddition strategy), was resolved by lactone opening with ( -)-(S)-1-phenylethylamine, chromatographic separation of the amides, and acid-mediated re-lactonization. Optically pure lactone (83) was converted into the sulphone (84) and this was coupled (by the sequence indicated here) to a chiral 'leftwing' tetrahydropyran-aldehyde (85), itself prepared from 1 ,6anhydro-P-D-glucose, to complete the formation of X-145471-2 (82).66 Another possible 'left-wing' precursor (86) has been prepared. 67 reaction on a pentaene that contains all of the carbon atoms of the full skeleton, and as a model for this strategy they have performed the cycloaddition of pentaene (87) to produce (88) as the major product.…”