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ChemInform Abstract The key step in the synthesis sequence shown in the scheme for the (S) enantiomer (VIII) of P-0160, an aryloxypropanolamine cardioselective β-blocker, is the reaction of the dioxolane (R)-(IV) with HBr in AcOH to give the acetoxy-bromo derivative (R)-(V). -Analogously, the (R) enantiomer of (VIII) is obtained starting from the (S) enantiomer of (I).

Oxidative and hydrolytic degradation reactions were carried out on teicoplanin in order to characterize the aromatic portion of the molecule and relate it to the other members of the class of glycopeptide antibiotics. Seven aromatic rings, obtained as triphenyl ether, diphenyl ether, and diphenyl moieties after oxidation and hydrolysis of teicoplanin, were identified. They are present in teicoplanin as aromatic amino acids and constitute the peptidic part of the molecule. The diphenyl ether and diphenyl moieties, which were isolated both as esters after oxidation and as a-amino acids after acid hydrolysis clearly indicate the nature of the corresponding amino acids in teicoplanin. The triphenyl ether moiety, which was isolated only as ester, allows the hypothesis that the corresponding amino acids are the same as those of the other glycopeptide antibiotics.Teicoplanin, a member of the class of glycopeptide antibiotics, is produced by Actinoplanes teichomviceticus as a group of very similar compounds which have the same aglycone containing aromatic aminoacidic moieties as well as D-mannose and D-glucosamineThis paper describes the completion of the oxidative and hydrolytic degradation reactions carried out in order to characterize the aromatic portion of the molecule and relate it to the other members of this class of antibiotics. Oxidative DegradationTeicoplanin was hydrolyzed with 2 N H,SO, and the reaction mixture, which accounts for the peptidie fragments of the molecule, was adsorbed on an anionic resin column (IRA-904 free base). After elution, the mixture was methylated with CH3I/K,CO3 to protect the free functions and treated with KMnO,/MgSO, to obtain a mixture of oxidation products.The crude mixture was methylated with diazomethane and chromatographed on a Silica gel column eluting with CHCI3 -MeOH, 98: 2. Two esters were obtained in significant amount: 1, M+ m/ 534 and 2, M+ m/z 346; a third one was isolated in trace amount: 3, M+ m/z 519. When teicoplanin as such was methylated and oxidized under the same conditions two main products were obtained: 4, M+ m/z 224 and 2. The structures of products 1 through 4 are assigned on the basis of spectral data in comparison with those of similar fragments isolated from other glycopeptide antibiotics.Structures of Compounds 1 and 3The MS spectrum of 1 shows molecular ions at m/z 534, 536, 538, whose ratio 9: 6: 1 indicate the presence of two chlorine atoms. The exact mass measurement (534.0484) indicates the elemental composition C25H20Cl2O9.The IR spectrum of 1 shows the presence of ester functions (1730 cm-1).

Die Reaktion von Rifamycin S (I) mit Cysteinamid (II) gibt das Thiazolrifamycin (IIIa).