di-(1-<(1R)-carboxy-2-methylpropyl>-(3R)-<-(5S)-5-amino-5-carboxypentanamido>-(4R)-mercapto azetidin-2-one)disulphide   、                                                                                      
1,4-二巯基-2,3-丁二醇                                                                                                                                                                                                                                                                                                          以70%的产率得到(S)-2-Amino-5-[(R)-1-((R)-1-carboxy-2-methyl-propylcarbamoyl)-2-(2,3-dihydroxy-4-mercapto-butylsulfanyl)-2-mercapto-ethylcarbamoyl]-pentanoic acid