The previously unreported alpha,alpha-disubstituted 1-aminoboronate esters have potential utility in peptidomimetic design, particularly against serine protease targets. A concise synthesis of 1-aminocyclopropaneboronate pinanediol ester is reported, and a peptidyl derivative is shown to have modest affinity (K(i) = 1.6 microM) for hepatitis C NS3 protease.