Enantioselective syntheses of (R)-antofine and (R)-cryptopleurine starting from a 3-phenanthrenylpropanal derivative are reported. Asymmetric α-amination of this aldehyde is carried out in the presence of D-proline, which constitutes the key step in the syntheses and resulted in the formation of the new stereogenic center with very high enantioselectivity (94% ee).The indolizidine and quinolizidine moieties in the target molecules are formed through Pictet-Spengler reaction. The current method is shorter and high yielding in comparison with a similar strategy used for the synthesis of these molecules using proline-catalyzed α-hydroxylation of the same aldehyde.
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