Ph. D. THESIS 2009

a b
Figure 14. 1 H NMR spectrum (CDCl3, fragment) of: a)compound 3 (300
MHz); b)compound 4 (500 MHz).
The overlapped signals corresponding to the protons of the carbobicycle are
located in the range 1.5-2.5 ppm of the spectrum, their assignment being
partially elucidated yet.
The 1 H NMR spectrum of compound 4 (Figure 14b) displays unique signals
(two singlets) for the axial and equatorial protons of the flexible dioxanic ring
(δ==3.66 ppm at position 2' and δ==3.78 ppm at position 4').
Despite of the flexibility of the heterocycle, the bromomethyl substituents
located at position 3' exhibits two doublets characteristic for an AB system
instead of a singlet as in the case of the methyl substituents in compound 3.
This fact is due to the diastereotopicity of the Ha and Hb protons belonging to
the CHaHbBr groups, which give different signals, so they are not rendered
equivalent by conformational equilibrium. The correct assignment was possible
only in the 2D Heteronuclear spectrum, where the 13 C NMR spectrum signal at
δ=35.66ppm (3'-CH2Br secondary prochiral carbon atom) is correlated with the
both doublets ascribed to the methylenic diastereotopic protons (δa=3.56 ppm
and δb=3.47 ppm) of the bromomethyl groups.
The 13 C NMR spectrum of compound 4 (Figure 15) shows ten well
separated signals, attributed by the means of the 13 C NMR ATP and 2D
heteronuclear NMR (HMBC and HSQC) spectra.
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