M. F. Mackay

Asymmetric Synthesis of a Homochiral D2-Isoxazoline Amino Acid Derivative

(2R)-4-Methylene-2-phenyl-3-propionyloxazolidin-5-one underwent 1,3-dipolar cycloaddition with 2,6-dichlorobenzonitrile oxide to give (5S,7R)-3-(2,6-diphenyl)-7-phenyl-6-propionyl-2,6-diaza-1,8-dioxaspiro [4.4] non-2-en-9-one, a protected isoxazoline amino acid. The reaction proceeded regiospecifically and with high stereoselectivity. The anti addition product predominated. The regiochemistry of addition was determined by nmr and the stereochemistry of addition was determined by X-ray analysis. The transition state energies for syn and anti addition were calculated using the semi-empirical AM1 method in the MOPAC package

Structural studies of some 1-polymethyleneimino-2,4-dinitrobenzenesand related compounds; crystal structure of 1-(cis-2′,6′-dimethylpiperidin-1′-yl)-2,4-dinitrobenzene

The ultraviolet and 1H n.m.r. spectra of some 1-polymethyleneimino-2,4-dinitrobenzenes and related compounds are discussed. The effect of trifluoroacetic acid on these spectra was also investigated; with 1-azetidinyl-2,4-dinitrobenzene, acid-catalysed ring opening was observed. The solid-state conformation of 1-(cis-2′,6′-dimethylpiperidin-1′-yl)-2,4-dinitrobenzene has been defined by single-crystal X-ray crystallography. Triclinic crystals belong to the space group P–1 with a 8.165(1), b 7.865(1), c 11.148(1) A, α 95.23(1), β 106.00(1), γ 92.63(1)˚ and Z 2. The structure was refined to a final R of 0.048 for the 2222 observed data. In the crystal, the phenyl ring adopts a slight boat conformation, while the amino and o-nitro groups are significantly twisted from the mean plane of the ring.