| 摘要 |
<p>A method is described for the preparation of a compound of formula (formula see on enclosed paper version) where R is a protective group of the amino groups of the amino acids; R' is a C1-C10 alkyl radical, an aryl, an aralkyl or a group ArX(CH2)m; where Ar is an aryl, X=O, S, NR''; R'' is a C1-C5 alkyl or aryl radical and m is an integer between 0 and 5; in which (a) the carboxyl group of a compound of formula (formula see on enclosed paper version) is activated by treatment with a group that is an activator of carboxyl groups; (b) the compound thus activated is made to condense with a trimethylsulphoxonium or tri-methylsulphonium ylide; (c) the keto-ylide thus obtained is reduced by reaction with a ketone-reducing agent; (d) the compound thus obtained is then cyclized to give the compound of formula IV by reaction with a base.</p> |
