47(P-5) ラン藻の産する鉄キレート物質シデロフォアの化学構造(ポスター発表の部)

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Iron is the most important transition metal for all organisms. It is well known that under iron deficient condition a large number of microorganisms secrete the low-molecular weight chelating compounds, siderophores, and acquire the iron-siderophore complex into cells with their outer membrane specific receptors. Cyanobacteria are the prokaryotic phytoplankton and the representative primary producer in aquatic environment. They perform oxygenic photosynthesis using various iron-containing catalysis, and many species of them can also fix nitrogen by the iron-rich enzyme, nitrogenase. However little is known about the molecular mechanism to acquire the iron of cyanobacteria. Last year, we reported the first genuine cyanobacterial siderophore, anachelin (1) and anachelin-2 (2), from Anabaena cylindrica NIES-19. We isolated a novel cyanobacterial siderophore, oscillabactin (3), from Oscillatoria tenuis UTEX1566. The molecular formula of 3 was determined to be C_<28>H_<34>O_<12>N_5 from HRFAB-MS analysis. 2D NMR analyses including COSY, HMQC, ^1H-^<13>C HMBC, and ^1H-^<15>N HMBC experiments, generated five units as follows; a salicylic acid unit (Sal), two β-alanine units (βAla(1) and βAla(2)), a 3-[2'-(2"-amino-1"-hydroxybutane-4"-yl)oxazole-4'-yl]-2,3-dihydroxypropionic acid unit (Ahoda), and a 1,2-dihydro-1,3-dihydroxy-2-oxopyridine unit (Ddop). ^1H-^<13>C HMBC correlations between these units constructed the sequence of Sal-Ahoda-βAla(1)-PAla(2)-Ddop. 3 is the first siderophore containing the hydroxypyridinone structure as the iron-binding group. And we studied the stereochemistry of Dmaq and Atha units in anachelins (1 and 2). 2 was methylated and hydrolyzed to obtain MeDmaq unit. Absolute configuration at C3 of MeDmaq was assigned as S on the basis of the Boc-phenylglycine method. 1 was converted to the 1,3-O-isopropylidine derivative and the relative stereochemistry between C3 and C5 of Atha was determined to be syn by NOESY correlations. And irradiation of H7 (δH 4.00) of Atha in 2 gave the clear J value (6.4Hz) between H5 and H6 in the oxazoline ring. From comparison this with the reported values, we assigned the conformation of oxazoline ring of 2 to be trans.
天然有機化合物討論会の論文
2002-09-01

47(P-5) ラン藻の産する鉄キレート物質シデロフォアの化学構造(ポスター発表の部)

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