Determination of the relative configuration of tropinone and granatanone aldols by using TBDMS ethers

• Ryszard Lazny,
• Aneta Nodzewska,
• Katarzyna Sidorowicz and
• Przemyslaw Kalicki

Beilstein J. Org. Chem. 2012, 8, 1877–1883, doi:10.3762/bjoc.8.216

• already used for exo–endo isomerization of tropinone aldols [3]. Blocking of the hydroxy group with an ether or ester group would make formation of internal hydrogen bonding to the amine nitrogen or the carbonyl oxygen H-bond acceptors impossible, thus changing significantly the structure of aldols in

• and endo side chain (equatorial and axial α-CH, respectively). On the basis of the observed exo–endo isomerization, and trends in NMR data changes upon isomerization, we were fairly certain of the assigned stereochemistry of the new isomer as exo,syn-3. This procedure developed on tropinone aldols was

• was determined as exo,syn by comparison of NMR data of the aldol isomers, in particular vicinal coupling constants and shifts corresponding to the side-chain CH group, with data of related TBDMS derivatives and confirmed by single-crystal X-ray diffraction. Keywords: aldol reaction; exo–endo