The syntheses of the sterically hindered N,Nf-dihydroxyaminals; N,Nf-bis(1-ethoxycarbonyl-1-methylethyl)-N,N1-dihydroxymethanediamine, l b , and N,N'-bis(l,l-dimethylethyl)-N,N'-dihydroxymethanediamine, l c , and their reactions with phenylboronic acid to yield the 1,3,5-trioxa-6,s-diaza-2,4~diboracyclooctanes 3 and 4, respectively, are described. Crystals of l b are tetragonal, a = 18.413(1), c = 9.867(2) A, Z = 8, space group 14,; those of 3 are mono-