The syntheses of the sterically hindered N,N′-dihydroxyaminals; N,N′-bis(1-ethoxycarbonyl-1-methylethyl)-N,N′-dihydroxymethanediamine, 1b, and N,N′-bis(1,1-dimethylethyl)-N,N′-dihydroxymethanediamine, 1c, and their reactions with phenylboronic acid to yield the 1,3,5-trioxa-6,8-diaza-2,4-diboracyclooctanes 3 and 4, respectively, are described. Crystals of 1b are tetragonal, a = 18.413(1), c = 9.867(2) Å, Z = 8, space group I41; those of 3 are monoclinic, a = 20.420(4), b = 8.272(4), c = 17.851(5) Å, β = 117.34(1)°, Z = 4, space group C2/c; and those of 4 are monoclinic, a = 9.493(4), b = 16.202(4), c = 14.783(3) Å, β = 101.90(2)°, Z = 4, space group P21/c. The structures were solved by direct methods and were refined by full-matrix least-squares procedures to R = 0.034, 0.039, and 0.040 (Rw = 0.035, 0.034, and 0.036) for 1550, 1438, and 2187 reflections with I ≥ 3σ(F2), respectively. In the solid state, both 3 and 4 exhibit transannular [Formula: see text] interactions. In 3 there are two identical (by symmetry) interactions with [Formula: see text] Å that have estimated bond orders of 0.06, while the single transannular interaction in 4 has N—B = 1.953(3) Å and a bond order of about 0.3. The intermediate-strength transannular interaction in 4 is the first to be reported for this type of molecule.