A compund having the formula ##STR1## can be prepared by coupling a compound having the formula ##STR2## or a salt thereof, with a compound having the formula ##STR3## to yield a compound having the formula ##STR4## and oxidizing that compound to yield the desired compound; wherein R is hydrogen or an amino protecting group; R.sub.1 is hydrogen, methly or ethyl; M.sup..sym. is an inorganic cation or a substituted ammonium ion; and M.sub.1.sup..sym. is hydrogen, an organic cation, or a substituted ammonium ion.
具有公式##STR1##的化合物可以通过将具有公式##STR2##或其盐的化合物与具有公式##STR3##的化合物偶联,生成具有公式##STR4##的化合物并将该化合物氧化而制备得到所需的化合物;其中R是氢或
氨基保护基;R.sub.1是氢,甲基或乙基;M.sup..sym.是无机阳离子或取代
铵离子;M.sub.1.sup..sym.是氢,有机阳离子或取代
铵离子。