Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)A study of the aldol reactions of boron enolates from methylketones that are protected with dimethylacetonide or di-tert-butylsilyl groups and that possess a trans or cis relationship between the chiral centers is presented. The main objective of this work was to evaluate the influence of the relative stereochemistry between the chiral centers and the steric and electronic influences of the cyclic protecting groups on the aldol reactions. The aldol adducts were obtained with moderate to high 1,5-anti stereoselectivity that was dependent on both the identity of the protecting group on the beta,delta-oxygen stereocenters and the relative stereochemistry between the beta and delta chiral centers. A theoretical analysis of the transition states involving these aldol reactions was performed utilizing DFT (density functional theory).77837663792FAEP-UNICAMPFundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)CNPq [Proc. CNPq 573.564/2008-6]