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The existence of an isomeric form in equilibrium with the major component of FK-520 in polar solutions has been demonstrated. This minor component has been isolated in high yield and purity by a novel crystallization strategy and preparative HPLC. The equilibrium product was characterized by NMR and MS.

Proton magnetic resonance spectra at 100 MHz were obtained for water-soluble and water-insoluble glucans from 11 strains of Streptococcus mutans . The percentages of α- D -(1→6) and non-α- D -(1→6)-, namely, α- D -(1→3)-, linkages were calculated from the anomeric-proton resonances in the 4.7-4.8 and 5.0-5.1 p.p.m. range, respectively. The average content of α- D (1→6) linkages in the polymer fractions precipitating from solution during synthesis of the glucans was generally much lower than that of fractions remaining in solution. The frequent appearance of the α- D -(1→3) resonances as doublets in the spectra suggested neighboring-group effects among the possible α- D -(1→3) and α- D -(1→6) linkage-configurations. These effects were confirmed from 100-MHz spectra of products of a dextranase-degraded, water-insoluble glucan, and a 270-MHz spectrum of an undegraded glucan. It was thus possible to assign the doublet resonances to α- D -(1→3), homogeneous, heterogeneous, and branch configurations, although complete differentiation among proportions of each configuration in the glucan chains could not be achieved.

We have shown previously that the esters of adenosine-5'-carboxylic acid (10) represent a new class of potent nontoxic coronary vasodilators. For example, the ethyl ester (12), which is active by an intraduodenal or intravenous route in dogs, causes a large increase in coronary sinus PO2 and coronary blood flow. Because of the pronounced vasoactive properties of the esters of adenosine-5'-carboxylic acid, a systematic study of the corresponding amides (14--50) was undertaken. In addition, several other analogues containing the N1-oxide function (51--52) or 2',3' substituents (3--9, 53--54) were studied.

Several previously undescribed metabolites related to lankamycin have been isolated from fermentation broths of the lankamycin-producing organism Streptomyces violaceoniger. Two of these metabolites, of weak antibacterical activity, have been characterized as 15-O-(α-L-4-O-acetyl-arcanosyl)-lankamycin and 15-deoxy-15-oxo-lankamycin. The latter antibiotic is prepared in high yield by Jones oxidation of lankamycin.

The nature of the products obtained from the reaction of chelocardin (1) and the model compound 2-acetyldimedone (5) with a variety of amines was investigated. It was observed that amines react wit...