Allocoronamic acid

The spiropyrazohnes obtained from 51 were converted into enantiopure A -pyrazoline-3-carboxylates and 1 -(hydroxyethyl)cyclopropane-1 -carboxylates (128). Those obtained from 54 and 55 were transformed into optically active a-spirocyclopropyllactones and 3-amino-3-(hydroxyethyl)pyrrolidin-2-ones (130). The spiropyrazoline obtained from a chiral propylidene-diketopiperazine and diazomethane was converted into (+)-(lR,25)-l-amino-2-ethyl)cyclopropane-l-carboxylic acid (allocoronamic acid) (135). 

Biochemical reactions of l-amino-2-ethylcyclopropane-l-carboxylic acid showed strong stereoselectivity. Thus, ring-opening to 2-ketohexanoate was observed only with the (IS, 2S)-isomer (505) . On the other hand, cycloelimination to give butene by the ethylene forming enzyme in apples or pea epicotyls was performed preferentially with allocoronamic acid (649), the (IR, 2S)-isomer Pea epicotyl enzyme (cell-free system) catalyzed the formation of 1-butene for all stereoisomers (i.e. 505 and 649)" ... 

IR-Coronamic acid (505) and U -allocoronamic acid (649) were more effectively converted to the 1-malonyl derivative than the two IS-stereoisomers From this stereoselectivity it was deduced that aminocyclopropanecarboxylic acid (6) is recognized as a D-amino acid by malonyl transferase. For resolution of racemic 2-alkyl-1-aminocyclopropane-1-carboxylic acids see Refs 27, 33, 752. 

Asymmetric cyclopropanation of a chiral azalactone 27, derived from 1,2-0-isopropyhdene-D-glyceraldehyde, was effected successfully with diazomethane in the synthesis of allocoronamic acid, one of the aminocyclopropanecarboxylic acids useful for the control of enzymatic pro-... 

The second chirality source used in the synthesis of aminocyclopropane carboxylic acids was D-glyceraldehyde acetonide, which after Wittig-Homer-Emmons reaction provided the alkenes 61. Treatment with diazomethane and subsequent irradiation at low temperatures alforded the cyclopropanes 62, which were converted into several other derivatives by modification of the side chain (Scheme 11). Notably, the best results were obtained by irradiating in the presence of benzophenone as triplet sensitizer [33, 34]. Following a similar synthetic procedure allocoronamic acid 65 was prepared, which is one of the amino acids that can be processed by plant tissues and promises the possibility to control the enzymatic processes underlying plant growth and fruit ripening [35]. 

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