ORGLIST: borohydride reduction reaction workup

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From: diogo$##$unilavras.edu.br
Date: Sat Jul 30 2005 - 16:57:37 EDT


Hello you all!
I'm working on some glicoside-derived amines and I had problems concerning
to the final step: amination. I tried reductive amination with some
glicosides thru their formyl groups and using sodium cianoborohydride. As
the reactions didnīt shwo favorable I turned the metodology to the
sequence in which I first prepare an imine derivative and then it is
reduced to the correspondent amine compound. This reduction reaction
workup has been the problem: Iīm using sodium borohydride since itīs a
mild reagente (the glicoside linkage wouldnīt resist some other
reagents...)and catalytic hydrogenation led to hydrogenolysis of the
product. I am sucessfull with the reduction (TLC, NMR, IV) but the product
is as water soluble as the byproducts of reduction. Iīve been preparing
the imine in metanol and using the same solvent in reduction. although
itīs quite a small quantity of the impurity I need the compouns very pure
since they will be submitted to biological testes. How can I solve this,
please? I tried columm cromat. but only metanol elutes the product (and
"all" the silicagel)and I donīt have acess to many others stacionary
phases...
Iīll be thankfull with any help.
Diogo
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