主权项 |
1. A process for the preparation of a compound of formula Va or Vb wherein Pg is an amino protecting group, and Z is hydrogen, hydroxyethyl or a group convertible to hydroxyethyl, the process comprising the steps of: (i) reacting a compound of formula II′ wherein Pg is defined as above, with a compound of the formula VI or VII wherein Z is defined as above, to obtain a compound of formula IIIa′ or IIIb′, respectively wherein Pg and Z are as defined above, (ii) reducing the nitro group in the compound of formula IIIa′ or IIIb′ to an amino group to obtain a compound of formula IVa′ or IVb′, respectively, and (iii) nitrosation of the compound of formula IVa′ or IVb′ to obtain the compound of formula Va or Vb, respectively. |