Ribosides and Ribotide of a Fairy Chemical, Imidazole-4-carboxamide, as Its Metabolites in Rice

Abstract

The metabolism of imidazole-4-carboxamide (ICA) in plants has been unknown. Two metabolites (1 and 2) were isolated from ICA-treated rice, and their structures were determined by spectroscopic analysis including the single-crystal X-ray diffraction technique and synthesis. The ribotide of ICA (3), whose existence was predicted, was also synthesized and detected from the treated rice by LC−MS/ MS. These results indicated that rice might interconvert ICA, 1, and 3 to regulate the biological activity.

S-Adenosylhomocysteine Analogue of a Fairy Chemical, Imidazole-4-carboxamide, as its Metabolite in Rice and Yeast and Synthetic Investigations of Related Compounds

“…The DEPT experiment indicated the presence of three methylenes, seven methines, and three nonprotonated carbons. The 13 C NMR data (δ C 34.1, 72.8, 75.8, 84.8, 91.8, 121.4, 131.3, 136.9, 163.0) indicated that 8a had the same skeleton as that of ICAr . The ribose part (C-1′–C-5′) was constructed by the DQF-COSY correlations (H-1′/H-2′; H-2′/H-3′, 4′; H-3′/H-4′; H-4′/H-5′) and the HMBC correlations (H-1′/C-2′; H-2′/C-1′, C-4′; H-3′/C-1′, C-5′; H-4′/C-3′; H-5′/C-3′, C-4′) (Figure ).…”

“…The 13 C NMR data (δ C 34.1, 72.8, 75.8, 84.8, 91.8, 121.4, 131.3, 136.9, 163.0) indicated that 8a had the same skeleton as that of ICAr. 12 The ribose part (C-1′−C-5′) was constructed by the DQF-COSY correlations (H-1′/H-2′; H-2′/H-3′, 4′; H-3′/H-4′; H-4′/H-5′) and the HMBC correlations (H-1′/C-2′; H-2′/C-1′, C-4′; H-3′/C-1′, C-5′; H-4′/C-3′; H-5′/C-3′, C-4′) (Figure 3). The linkage position between the sugar and 2 was determined from the cross-peaks (H-1′/C-2 and H-1′/ C-5) (Figure 3).…”

“…After the selective removal of the methyl group of Lmethionine (12) by Birch condition, without purification of the produced homocysteine, oxidative dimerization with hydrogen peroxide proceeded smoothly to provide the stable homocystine. 13 In order to accomplish the efficient C−S bond formation of 8a, 14,15a the protection of the carboxy and amino groups by methyl esterification and incorporation of a Boc group provided 13.…”

“…After removing the solvent of each extracts under reduced pressure, they were dissolved in 5% MeOH and subjected to HPLC analysis. The extracts were analyzed by reversed-phase HPLC using a Develosil C30-UG-5 column (ϕ 4.6 mm × 250 mm, 5 μm) with a gradient manner (5% MeOH (B) in (A) for 30 min, 5%−100% B in A for 45 min, and 100% B for 30 min) at a flow rate of 0.5 mL/min at a multiple wavelength using a photodiode array detector 12 (Figure S1, Supporting Information).…”

“…We hypothesized that FCs are a new family of plant hormones, and the clarification of the metabolic pathways of FCs is important to substantiate the hypothesis. ,− A riboside of ICA (ICAr, 5 ) and a glucoside of 5 ( 6 ) have been isolated from ICA-treated rice, and endogenous existence of 5 and a ribotide of ICA ( 7 ) in rice has been proved (Figure ). The metabolites showed no or weak activity against plant growth, suggesting that the interconversion between FCs and their glycosides regulated the homeostasis of rice. In the course of our continuing search for metabolite(s) of 2 from rice, we found a new metabolite 8a .…”