Dear Dr. P. Merino,
the ozonization of 4a into 5a was followed by t.l.c. and
DMS was added at -78 C when 4a disappeared. However very
polar products were formed (the yield is 78% only), but
their structure was not investigated.
Concerning the removal of N-benzyl group from the amide
6a, we observed that it can be performed only by using
Li-NH3 (see Orena, Porzi, Sandri, J. Chem. Res., (S),
1990, 376, and cited references): In fact the substrate
6a could not be debenzylated by hydrogenolysis, even by
treatment with H2-Pd(OH)2, so that we choosen to convert
the amide 6a into the amine 7a, in order to remove the N-
benzylic group.
Prof. Mario Orena