Reaction SMILES: [CH3:1]/[CH:2]=[C:3]1\[C:4]2[S:8][CH2:7][CH:6]([C:9]([NH:11][CH:12]([C:108]([OH:113])([CH:110]([OH:112])[CH3:111])[CH3:109])[C:13]3[S:17][CH:16]=[C:15]([C:18]([NH:20][CH:21]4[C:60]5=[N:61][C:57](=[CH:58][S:59]5)[CH:56]5[N:62]=[C:63]([C:65]6[S:69][CH:68]=[C:67]([C:70]([NH:72][C:73]([C:75]([NH:77][C:78]([C:80]([NH2:82])=[O:81])=[CH2:79])=[O:76])=[CH2:74])=[O:71])[N:66]=6)[CH2:64][C:54]([C:83]6[S:87][CH:86]=[C:85]([C:88]([NH:90][CH:91]([CH:95]([OH:97])[CH3:96])[C:92]([NH:94]\1)=[O:93])=[O:89])[N:84]=6)([CH2:55]5)[NH:53][C:51](=[O:52])[CH:50]([CH3:98])[NH:49][C:47](=[O:48])[C:45](=[CH2:46])[NH:44][C:42](=[O:43])[C:40](=[CH2:41])[NH:39][C:37](=[O:38])[CH:36]([CH:99]([CH3:101])[CH3:100])[NH:35][CH:32]1[CH:33]([OH:34])[C:28]5=[C:29]([C:102]([CH:104]([OH:106])[CH3:105])=[CH:103][C:26](=[N:27]5)[C:24](=[O:25])[O:23][CH:22]4[CH3:107])[CH:30]=[CH:31]1)=[O:19])[N:14]=3)=[O:10])[N:5]=2.[C:114]1(=[O:120])[O:119][C:117](=[O:118])[CH2:116][CH2:115]1.[OH2:121].C(Cl)(Cl)Cl>N1C=CC=CC=1>[CH3:1]/[CH:2]=[C:3]1\[C:4]2[S:8][CH2:7][CH:6]([C:9]([NH:11][CH:12]([C:108]([OH:113])([CH:110]([OH:112])[CH3:111])[CH3:109])[C:13]3[S:17][CH:16]=[C:15]([C:18]([NH:20][CH:21]4[C:60]5=[N:61][C:57](=[CH:58][S:59]5)[CH:56]5[N:62]=[C:63]([C:65]6[S:69][CH:68]=[C:67]([C:70]([NH:72][C:73]([C:75]([NH:77][C:78]([C:80]([NH2:82])=[O:81])=[CH2:79])=[O:76])=[CH2:74])=[O:71])[N:66]=6)[CH2:64][C:54]([C:83]6[S:87][CH:86]=[C:85]([C:88]([NH:90][CH:91]([CH:95]([OH:97])[CH3:96])[C:92]([NH:94]\1)=[O:93])=[O:89])[N:84]=6)([CH2:55]5)[NH:53][C:51](=[O:52])[CH:50]([CH3:98])[NH:49][C:47](=[O:48])[C:45](=[CH2:46])[NH:44][C:42](=[O:43])[C:40](=[CH2:41])[NH:39][C:37](=[O:38])[CH:36]([CH:99]([CH3:100])[CH3:101])[NH:35][CH:32]1[CH:33]([OH:34])[C:28]5=[C:29]([C:102]([CH:104]([OH:106])[CH3:105])=[CH:103][C:26](=[N:27]5)[C:24](=[O:25])[O:23][CH:22]4[CH3:107])[CH:30]=[CH:31]1)=[O:19])[N:14]=3)=[O:10])[N:5]=2.[C:117]([OH:119])(=[O:118])[CH2:116][CH2:115][C:114]([OH:120])=[O:121]
Reactant: O
Reactant: O=C1CCC(=O)O1
Agent: C=C(NC(=O)C(=C)NC(=O)c1csc(C2=NC3CC4(C2)NC(=O)C(C)NC(=O)C(=C)NC(=O)C(=C)NC(=O)C(C(C)C)NC2C=Cc5c(C(C)O)cc(nc5C2O)C(=O)OC(C)C(NC(=O)c2csc(n2)C(C(C)(O)C(C)O)NC(=O)C2CSC(=N2)/C(=C\C)NC(=O)C(C(C)O)NC(=O)c2csc4n2)c2nc3cs2)n1)C(N)=O
Solvent: c1ccncc1
Solvent: ClC(Cl)Cl
Product: O=C(O)CCC(=O)O

Procedure:
Siomycin A (10.0 g) is dissolved in pyridine (60 ml) and butanedioic acid anhydride (6.0 g) is added to the mixture. The resultant mixture is kept with stirring at 93° to 95°C for an hour in oil bath. Distilled water (60 ml) and chloroform (100 ml) are added to the reaction mixture, and then the resultant solution is vigorously shaken. The chloroform phase is evaporated under reduced pressure to remove the solvent, then benzene is added to the resulting residue. The benzene-insoluble part is dissolved in a mixture of chloroform and methanol (8 : 2 by volume). The resulting mixture is chromatographed on a column of silica gel (particle size 0.05-0.2 mm, made by Merk company) and eluted with a mixture of chloroform and methanol with a progressively increasing concentration of methanol. The fractions containing the half ester of siomycin A with butanedioic acid are collected and concentrated. The concentrated solution is applied to a silica gel GF plate (made by Merk company) and the plate is developed with a mixture of chloroform and methanol (8 : 2 by volume). The part containing the half ester -I of siomycin A with butanedioic acid is extracted with a mixture of chloroform and methanol and the resulting solution is concentrated. To the concentrated solution is added ethyl acetate to obtain the half ester of siomycin A with butanedioic acid (precipitate). The yield is 60%.