Table 1. Computed Relative Stabilities of Methyl Boronic Acid Esters Derived from Steroids 1–3 (DFT, B3LYP, 6-31+G*).

	realtive energy for the regioisomeric boronates (DFT, B3LYP, 6-31+G*) (kcal/mol)
scaffold	C1/C3	C1/C5	C1/C11	C1/C19	C3/C5	C3/C19	C5/C19	C11/C19
1a	+8.3	+8.9	+7.6	0	+7.8	+18.3	+2.3	+7.6
2b	-	-	-	-	+1.9	+22.2	0	-
3c	-	-	-	-	+1.7	+17.2	0	-

^aReferenced to the energy of cyclic C3/C5 boronate derived from 1.

^bReferenced to the energy of cyclic C5/C19 boronate of 2.

^cReferenced to the energy of cyclic C5/C19 boronate derived from 3.