| abstract |
A compound of formula (I) wherein R?1 and R2¿ are each (CH¿2?)mX, R?3¿ is H, each X is Cl or Br and m is 2 or 3, in combination with less than 0.5 % w/w of the corresponding compound wherein R1 is (CH¿2?)mH. Such compounds can be prepared by (i) the reaction of a Bronsted acid or a Lewis acid with NaBH4 in an organic solvent, and (ii) adding the resultant solution to a solution of a corresponding compound wherein one of R?1 and R2¿ is CO(CH¿2?)nX and the other is CO(CH2)nX or (CH2)mX, wherein n = m-1. Such compounds can also be prepared, in optically-enriched form, starting from an optically-enriched trihaloiminophosphorane of the formula R*N = Phal3 wherein NR* is a chiral moiety derivable from a chiral amine or chiral sulphonamide of the formula R*NH2, which can be cyclisable with HO(CH2)3NHR. |