Aminocyclopropanecarboxylic acid and derivatives

FIGUR E19. Bond lengths (A) and bond angles (deg) in 1-aminocyclopropanecarboxylic add (74). Mean values are shown as calculated from the reported data133 

FIGURE 21. Sketch of molecule A in the crystal of hexa-methyl cyclopropanehexacarboxylate (85) 

1-Aminocyclopropanecarboxylic acid (74) has attracted special interest (a) as a modified model of natural a-amino acids, in the synthesis of bioactive peptide analogs, potential enzyme inhibitors , or e.g. a derivative with sweetness receptor activity s and (b) together with its Schiff-base metal complexesas the biosynthetic precursor of ethene, the plant ripening hormone . (See these sources and the review in Reference 135 for further references.) 

FIGURE 20. The conformation of and intramolecular hydrogen bond in the dipeptide ester H—(Ac3c)2—OMe (81). Dihedral angles (deg) of the H2N—C—C(0)—N—C—C(0)—O—Me chain are indicated 

Ring formation in cw-cyclopropane-l,2-dicarboxylic anhydride s (84) leads to ac conformation of the C=0 groups, rotated by 155° from syn, and to strikingly narrower (and unequal) bond angles C2—Cl—C(0) 105.6 (2)° and C3—Cl—C(0) 113.4 (2)° than in the parent diacid 63c (Table 5). Bond lengths of 84, Cl—C21.505 (3), Cl—C3 1.497 (3), C—C(0) 1.470 (2) A, have somewhat changed relative to 63c. The molecule lies on a crystallographic mirror plane. 

---