Crystal structures of chiral 2-[bis-(2-chloro-eth-yl)amino]-1,3,2-oxaza-phospho-lidin-2-one derivatives for the absolute configuration at phospho-rus

'Nitro-gen mustard' bis-(2-chloro-eth-yl)amine derivatives (2 ,4 ,5 )- and (2 ,4 ,5 )-2-[bis-(2-chloro-eth-yl)amino]-3,4-dimethyl-5-phenyl-1,3,2-oxaza-phos-pho-lidin-2-one ( and , respectively), C H Cl N O P, and (2 ,4 )- and (2 ,4 )-2-[bis-(2-chloro-eth-yl)amino]-4-isobutyl-1,3,2-oxaza-phospho-lidin-2-one ( and , respectively), C H Cl N O P, were synthesized as a mixture of diastereomers through a 1:1 reaction of enanti-omerically pure chiral amino alcohols with bis-(2-chloro-eth-yl)phospho-ramidic dichloride. Flash column chromatography yielded diastereomerically pure products, as supported by P NMR. The crystal structures of and were obtained to determine their absolute configuration at phospho-rus, and P NMR chemical shift trends are proposed based on the spatial relationship of the bis-(2-chloro-eth-yl)amine moiety and the chiral substituent of the amino alcohol. Oxaza-phospho-lidinones were observed to have a more downfield P NMR chemical shift when the aforementioned substituents are in a configuration and for when they are .