New aspect of thermodynamic stability of 3-C-nitro-d-glucal derivatives

Communication: Double Bond Migration of a 1,5-Anhydro-3-C-p-Tolylsulfonyl-D-Hex-2-Enitol Derivative and the Corresponding 5a-Carba-Dl-Sulfonyl Sugar

“…However, this delocalization is less effective than with the SO 2 Me nitro sugar; for example, donor acceptor stabilization 9 between Hoc a n d °*c-s is 28.1 kJ/mol for the allal 10, while that between rcc=c and C* C -N is 49.8 kJ/mol for the corresponding 3-C-nitroallal. 10 It was noteworthy that the double bond migration of 3-C-nitro-2-enitol 3 gave the D-glucal 4 as a preliminary product, which then epimerized to afford a 2.5 : 1 equilibrium mixture of D-glucal 4 and D-allal 5." However, in the correspondingsulfonyl sugar 8 the D-allal 9 was first formed, and then epimerized to give a 1 : 8.4 equilibrium mixture of the D-allal 9 and the D-glucal 11.…”