Symposium on the Chemistry of Natural Products, symposium papers

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The reaction of benzoic acid with alcohols, diethyl azodicarboxylate (I) and triphenylphosphine (II) resulted in the formation of the corresponding alkyl benzoates in good yields, Similarly, phosphorylation of alcohols took place when phosphate esters were used in the place of benzoic acid in this reaction, The reaction would proceed through an alkoxy phosphonium salt (V) which in turn decomposed to the esters and triphenylphosphine oxide. Verification of this hypothesis was obtained as follows. When (S)-(+)-2-octanol was allowed to react with benzoic acid, I and II, (R)-(-)-2-octyl benzoate was obtained. The nearly complete inversion of the configuration of 2-octyl group would be best explained by assuming the formation of V. These reactions could be utilized in selective acylation and phosphorylation of 5^1-hydroxyl group of nucleosides. When thymidine was allowed to react with benzoic acid and p-substituted benzoic acids in the presence of Iand II in HMPA at room temperature, there were obtained the corresponding 5^1-O-aroylthymidines in good yields. The reaction of thymidine with dibenzyl hydrogen phosphate, I and II in THF at room temperature, followed by catalytic hydrogenolysis afforded thymidine 5^1-phosphate in a 47% yield. The yield of the thymidine 5^1-phosphate increased to 77% when the reaction was carried out in dioxane at 60℃. Similarly, phosphorylation of uridine in dioxane at 60℃ afforded uridine 5^1-phosphate in a 63% yield.

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The structure of a new antibiotic, ikarugamycin (IM) (1) was proposed based on the following degradation reactions. Catalytic hydrogenation of IM afforded a hexahydro IM (2), which gave a deoxyoctahydro IM (3) on further hydrogenation. Both (2) and (3) were reduced to a deoxydecahydro IM (4) by lithium borohydride reduction. Ozonolysis of IM followed by acid hydrolysis afforded L-ornithine and (5). Starting from (3), α-DNP-ornithine and (9) were obtained as shown in the scheme. Oxidation of IM with permanganate yielded (15), (16), (17), (18), (14) and (5), and with chromic acid (15), (16), (17), (19), (20) and (21). Both (2) and (3) gave (16), (17), (22), (23), (24), (25) and (26) on chromic acid oxidation. However, (27) and (28) were obtained only from (3).

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