Methods of preparing hydroxylamine derivatives useful in the preparation of anti-infective agents

A process for preparing a compound of Formula I, or a salt thereof:

• which comprises a reduce/couple sequence or a couple/reduce sequence,
• wherein:
• the reduce/couple sequence comprises
• (E1) reducing a compound of Formula V
• or an acidic or basic salt thereof,
• to obtain a compound of Formula VI
• or an acidic or basic salt thereof;
• and
• (F1) coupling the compound of Formula VI, or an acidic or basic salt thereof, with a compound of formula VII
• or a salt thereof;
• to form the compound of Formula I, or a salt thereof;
• the couple/reduce sequence comprises
• (E2) coupling a compound of Formula V:
• or an acidic or basic salt thereof,
• with a compound of Formula VII
• or a salt thereof,
• to obtain a compound of Formula VIII
• or a salt thereof;
• and
• (F2) reducing the compound of Formula VIII, or a salt there, to form the compound of Formula I, or a salt thereof;
• PG1 is an amine protecting group which forms with the amino nitrogen to which it is attached a carbamate, a benzylamine, or a sulfonamide;
• and
• PG2 is an oxygen protecting group selected from acetyl (Ac), benzyl (Bn), 4-MeOBn, benzoyl (Bz), and tert-Butyldimethylsilyl ether (TBS).