[g_orbital]

My question deals with a recent communication titled "Enantiospecific Total Syntheses of Kapakahines B and F" (JACS, 2009, 131, 6360, DOI: 10.1021/ja901573x), a work of Prof. Phil S. Baran from Scripps.

In scheme 2 (see the attached image file) the tryptophan-derivative 3 is converted into aminoacetal 7 using o-iodoaniline and NIS (Scheme 2). The coupling leads exclusively to a single diastereomer, namely the exo isomer. I wonder what is the controlling factor directing this unique diastereoselectivity. Does this have to do with the kinetic/thermodynamic conditions?

Also, the hydrogenolysis of compound 8 produces compound 9, which is said in the text to be more accessible. The latter is rearranged into the more reactive, difficult to access, isomer 10 possessing the primary amine. In your opinion, what makes isomer 10 more "difficult to access"?

 
Thanks in advance.

[orgopete]

My question deals with a recent communication titled "Enantiospecific Total Syntheses of Kapakahines B and F" (JACS, 2009, 131, 6360, DOI: 10.1021/ja901573x), a work of Prof. Phil S. Baran from Scripps.

Also, the hydrogenolysis of compound 8 produces compound 9, which is said in the text to be more accessible. The latter is rearranged into the more reactive, difficult to access, isomer 10 possessing the primary amine. In your opinion, what makes isomer 10 more "difficult to access"?

The intermediate preceding 10 is the iminium salt. It can react with either the just released amino nitrogen or the amide. The electrons of the amino group should be more reactive, hence react more quickly to give 9. That would make 10 more "difficult to access".