A CONVENIENT PROCEDURE FOR THE SYNTHESIS OF 2,3,4,6-TETRA-O-BENZYL-D-GLUCONOLACTAM AND D-NOJIRILACTAM

Swern oxidation of 2,3,4,6-tetra-O-benzyl-D-glucose (1) followed by am monolysis gave the crystalline amide 3 which was oxidized (DMSO/pyridi ne . SO3) to yield the oxo-amide 4 and the hydroxy-lactams 5 and 6. Cy clization of 4 to the very slowly equilibrating 5 and 6 was completed by treatment with AcOH in CHCl3. The configuration of the hydroxy-lact ams was assigned on the basis of NOEs. Reduction (Et3SiH/BF3 . Et2O) o f the hydroxy-lactams either individually or as a mixture led to 2,3,4 ,6-tetra-O-benzyl-D-gluconolactam (7). The procedure, based upon modif ications of a patent, does not require chromatography; the overall yie ld of 7 from 1 is 43%. Hydrogenolysis of 7 gave D-nojirilactam (8); be nzylation led to the known pentabenzyl-D-nojirilactam (9) and to the u nsaturated lactam 10.