Dear Dr. Orera,
I have read your contribution and I have some questions concerning the synthetic
elaboration of compound 3a into 8a.
Concerning the transformation of 4a into 5a (ozonization), what was the final
treatment? I think that you used dimethylsulfide. However, under such conditions
we have observed concomitant oxidation of benzylic positions in a variety of
compounds. Did you observe some kind of oxidation at the N-protecting group?
Concerning the elimination of the N-protecting group by hydrogenolysis of
compound 7a after reductive elimination of the amidic carbonyl, is it factible
carried out that reaction prior to the elimination of the carbonyl, i.e. on
compound 6a? It is known that N-benzyl lactams are much more difficult of
debenzylating that amines. In fact, we have find some trouble in a similar
reaction. Maybe you have tried debenzylation on 6a and can help us.
Thanking you in advance,
Yours sincerely,
***************************************
Dr. P. Merino
Departamento de Quimica Organica
Facultad de Ciencias
Universidad de Zaragoza
Plza. San Francisco s/n
E-50009 Zaragoza (Spain)
Tfno.: + 34 76 551208
Fax: + 34 76 567920
E-mail: pmerino@msf.unizar.es