The structure of concanamycin A was proposed on the basis of PMR analyses of concanamycin A and its ozonolysis products.
In the preceding paper, concanamycin A (1) was subjected to alkaline degradation to afford the anhydroaglycone Pl and the sugar Sl, and their structures were described. 1
In order to elucidate the mode of binding of these components,ozonolysis of ( ) was performed and a degradation product containing Sl and a fragment of Pl was obtained.
In this paper, we describe the structures of the ozonolysis products and concanamycin A itself. Concanamycin A (1) crystallized from aqueous methanol as colorless crystals; m.p. 162-163.5 'C, C46H75NO14, IB-MS M+ m/z 865, hray 245 (E 40500), 284 nm (E 19300), vmax CHC13 3560-3500, 3420, 1718, 1690, 1585, 1455, 1385, 1363 cm -l, r4; -21.7' (c 1, methanol). Ozonolysis of (1) in methanol followed by reduction with dimethyl sulfide afforded three main products, Ozl (2a), 022 (2b), and 023 (3). 021 (2a); C14H2604, GC-MS m/z 226 (M-MeOH), vmax CHC13 3520, 1710, 1465, 1370 cm -l, [cl; -124.2" (c 1.29, acetone); was subjected to PMR analysis (Table I), and the structure was determined as depicted in Fig. 2. Clearly, the carbon chain of Ozl corresponds to that from C-5 to c-12 of Pl. The coupling constants of vicinal protons in the pyranose type structure revealed the relative configurations as shown in Fig. 2, indicating the equatorial configuration of the anomeric proton (u-anomer).