a Free energy of the α − anomer (kJ/mol); b Free energy of the β − anomer (kJ/mol); † Ref. 63 ; ‡ Ref. 62 ; § Ref. 67. A positive value of the difference denotes the $^{4}$C$_{1}$ as the most stable conformer Method Δ G [ α ] b Δ G [ β ] b Molecular mechanical † − 0.08 3.77 Semiempirical ‡ − 2.09 5.43 NMR § − 4.0 3.4 TABLE II: Theoretical and experimental estimates of idose inverted chair free energy.