(4R)-4-Benzyl-3-{(4S)-4-chloro-4-[(S)-2,2-dimethyl-1,3-dioxolan-4-yl]butanoyl}-1,3-oxazolidin-2-one

The title compound, C19H24ClNO5, was synthesized and subsequently employed in an Evans alkylation. The purpose was to prove the absolute configuration in the projected synthesis of the side chain of (–)-Lytophilippine A. The oxazolidinone and the isopropylidene acetal rings have twisted conformations. The oxazolidinone and side-chain carbonyl groups are orientated in an antiperiplanar arrangement to minimize van der Waals repulsions. Furthermore, the Cl atom and the acetonide-protected secondary alcohol are also in an antiperiplanar arrangement with a torsion angle of 173.64 (14)°. The absolute configuration was determined and agrees with the configuration of the used chiral auxiliary.

The title compound, C 19 H 24 ClNO 5 , was synthesized and subsequently employed in an Evans alkylation. The purpose was to prove the absolute configuration in the projected synthesis of the side chain of (-)-Lytophilippine A. The oxazolidinone and the isopropylidene acetal rings have twisted conformations. The oxazolidinone and side-chain carbonyl groups are orientated in an antiperiplanar arrangement to minimize van der Waals repulsions. Furthermore, the Cl atom and the acetonide-protected secondary alcohol are also in an antiperiplanar arrangement with a torsion angle of 173.64 (14) . The absolute configuration was determined and agrees with the configuration of the used chiral auxiliary.
Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: FF2045).
center at C23. The synthesis of I was carried out from carboxylic acid and (R)-4-benzyloxazolidin-2-one.
The oxazolidinone ring adopts a nearly coplanar conformation and the isopropylidene acetal is an open envelope-like structure. The oxazolidinone-and side-chain carbonyl groups are orientated in an antiperiplanar arrangement to minimize van der Waals repulsions. The dihedral angle between the plane through N, C10, O2 and the plane through N, C11, O3 is 9.4 (4)°. Furthermore, the chlorine atom and the acetonide protected secondary alcohol are also in an antiperiplanar arrangement with an torsion angle of 173.64 (14)°. The absolute configuration was determined and agrees with the configuration of the used chiral auxiliary.

Refinement
The hydrogen atoms were placed in calculated posions with C-H bond distances in the range from 0.95 to 1.00 Å and refined as riding on their parent atoms with U iso = 1.2 or 1.5 x U eq (C).