The reaction of cyclic and open-chain diastereomerically pure secondary organoboranes with diisopropylzinc allows the preparation of secondary dialkylzinc reagents with good to excellent retention of configuration as shown by deuterolysis and CuI- and Pd0-mediated reactions with electrophiles. The importance of a high boron-zinc exchange rate to obtain high diastereoselectivity has been shown. Improvement