Abstract
The asymmetric three-component coupling of α,β-unsaturated esters and alkylidene malonates initiated with a homochiral lithium amide proceeds with high levels of diastereoselectivity, with hydrogenation of the resultant α-substituted β-amino acid derivatives giving a range of differentially protected 3,4,5,6-tetrasubstituted piperidinones with four contiguous stereogenic centres.
Key Words
conjugate addition - three component coupling - oligomerisation - piperidin-2-one
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18 X-ray crystal structure determination for 15 : Data were collected using an Enraf-Nonius DIP2000 diffractometer with graphite monochromated Cu-Kα radiation using standard procedures at 100 K. The structure was solved by direct methods (SIR92), all non-hydrogen atoms were refined with anisotropic thermal parameters. Hydrogen atoms were added at idealised positions. The structure was refined using CRYSTALS. X-ray crystal structure data for 15 [C38 H43 NO4 ]: M = 577.76, orthorhombic, space group P 21 21 21, a = 11.2640 (2) Å, b = 16.6340 (3) Å, c = 17.0480 (2) Å, V = 3194.21 (9) Å3 , Z = 4, µ = 0.077 mm-1 , colourless block, crystal dimensions = 0.4 × 0.4 × 0.5 mm. A total of 3793 unique reflections were measured for 3<θ<27 and 3618 reflections were used in the refinement. The final parameters were w
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