Terpenoid chemistry. XXII. The trans,trans- and cis,cis-nepetalinic acids

Abstract

A study of the trans, trans-nepetalinic acids has resolved the numerous discrepancies in the literature concerning the physical constants of these reference compounds and has correlated these properties and the stereochemistry of the two epimers. Thus (2S,2?S,3?S)-2(2?-carboxy-3?- methylcyclopentyl)propanoic acid shows m.p. 123.4-123.6°, [α]_D -39° (1%, CHCl₃+1% EtOH) and the (2R,2?S,3?S) epimer, m.p. 121.5-122°, [α]_D -52° (1%, CHCl₃+1% EtOH), or m.p. 142-143° for the (±)-acid.     The cis,cis-nepetalinic acids have also been prepared and their stereochemistry assigned as (2S,2?R,3?S), m.p. 157-158°, [α]_D +18.6° (1%, CHCl₃+1% EtOH), and (2R,2?R,3?S), m.p. 68°, [α]_D -36° (1%, CHCl₃+1% EtOH).