Imndazolidine-derived phosphona esters (1.11) are prepared from 1-butyl (R)-2-1-butyl-3methylimidazolidin-4-one-I-carboxylate (Boc-BMI, A) by Michnelis-Arburov reactions of appropriate mtermediates [the 5-bromo-Boc-BMI and the acetary derivative (lo)].Deprotonation (DBULiBr or LTMPIBuLi) and reaction ~8 t h alkyl halides give gem, disubstituted heterocycles (3-7.12.17).some of which are converted to the corresponding 2-amino-2-aminomethylalkanephosphonic acids (8.9.18-21).One of the substitution reactions with P(0Me)j occurs with migration of the heterosubstituent from the a-NBoc to the a-NMe position of the ~midazolidine system (Scheme 4) A very surprizing reversal of the stereochemical course of alkylation is observed with the dimethyl imidazolidinephasphonate (11) upon going from the more reactive (MeI.BnBr, AllylBr) to the less reactive halides (Et-, Pr-, and BuI).The product structures are derived from three X-ray cryslal suucture analyses, by nmr companson.and by chemzcal correlation.
No takes yet. Share an insight, caveat, or question.
Seebàch et al. (1995) studied this question.