Stereoselective synthesis of cyclobuyl a-aminocyclopropylcarboxylic acids.

Article

Summary *

The highly stereoselective cyclopropanation of chiral cyclobutyl dehydro amino acids, synthesized from (-)-α-pinene or (-)-verbenone, has been achieved by means of a 1,3-dipolar cycloaddn. with diazomethane. The proximity of the double bond to the neighboring stereogenic center of the cyclobutyl moiety is crucial to obtain cyclopropanes as single diastereomers whose configuration has been detd. by X-ray structural anal. DFT theor. calcns. of the more stable conformations allow us to understand the π-facial diastereoselection as the result of steric hindrance by the gem-di-Me substituents and the side chain of the cyclobutane-ring. Chiroptical properties of these products have been studied by ORD and CD techniques and their behavior in CSA-NMR expts. has been ascertained. Information provided by the agent in SIGEVA