Ent-Kaurenate

Ent-kaurene Diterpene Glycosides from the Leaves of Stevia rebaudiana... 

Moore, T. C., H. Yamane, N. Muro-fushi, and N. Takahashi. Concentrations of ENT-kaurene and squalene in vegetative rice shoots. J Plant Growth Regul 1988 7(3) 145-151. 

Diterpenoid Alkaloids.—The structure and synthesis of the diterpenoid alkaloids have been reviewed. The subject is also covered in detail in the Specialist Periodical Report on the Alkaloids. A number of new alkaloids with the ent-kaurene skeleton have been isolated from Anopterus glandulosus and A. macleayanus. The structure of the major alkaloid anopterine (104) was assigned ... 

Other experiments with Gibberellafujikuro] the fungus that produces gibberellin, indicate that GA3 production is blocked by BAS 111. Very detailed and careful experiments conducted with enzymes in cell-free systems strongly support this mode of action, ie, using ent-kaurene oxidase and cinnamate 4-mono-oxygenase isolated from pea apices and soybean suspension cells, and flavanone-2-hydroxylase and dihydroxypterocarpane 6-hydroxylase from soybean suspension cells (31). 

Solvent Pimaradiene Pimarol Pimaric Isopimara- Isopimarol Isopimaric ent-Kaurene Podo- Manool... 

Microbiological Methods. The low substrate specificity of many of the enzymes involved in GA biosynthesis in Gibberella fujikuroi has been utilized for the preparation of higher plant GAs. Suitable analogs of the natural GA-precursors are converted by the fungus to the corresponding GA analogs. It is usual to prevent the synthesis of the natural GAs in order to facilitate purification of the unnatural products. A mutant strain, Bl- la, in which GA biosynthesis is blocked early in the pathway (67) (between ent-kaurenal and ent-kaurenoic acid) has been used. 

It is also possible to block GA synthesis chemically using inhibitors such as AMO-l6l8 (68), or the quaternary ammonium iodide compound in Figure 11 X 9,70), which block ent-kaurene formation. 

Figure 1. Numbering system for ent-kaurene and the GA s (GA,S) and the structures of ent-kaurene, GAn, GAS, and GA3...

After production of ent-kaurene, carbon-19 is sequentially oxidized to give ent-kaurenol, ent-kaurenal, and ent-kaurenoic... 

In peas (Pisum sativum) the complete pathway has been demonstrated from MVA through ent-kaurene and GA -al ehyde (see Figure 2) to 13-hydroxylated Cpo GAs (Figure 7) ( 1, -2) ... 

Figure 8. The ent-kaurene synthetase system and the d5 lesion of maize, Zea mays. Apparently the ds lesion favors the loss of the proton from carbon-15 rather than from carbon-17 as is the case for normal maize. Compounds in parentheses are hypothetical intermediates. The GA s identified by GC-MS were obtained from young maize tassels (57).

Murphy, G.J.P., Briggs, p-E. "Metabolism of ent-kaurenpl-17 l C, ent-kaurenal-17- and ent-kaurenoic acid-17- C by germinating Hordeum distichon grains." Phytochemistry,... 

Moore, T.C., Coolbaugh, R.C. "Conversion of geranyl-geranyl pyrophosphate to ent-kaurene in enzyme extracts of sonicated chloroplasts." Phytochemistry, 1976, 15, 12kl 12k7. 

Hedden, P., Phinney, B.O. "Comparison of ent-kaurene and ent-isokaurene synthesis in cell-free systems from etiolated shoots of normal and dwarf-5 maize seedlings."... 

The retardation effect of all these substances can be reversed by gibberellins. Furthermore, it has been possible, in the case of some of these substances, to detect precisely the point of attack or site of action in the gibberellin biosynthesis sequence. As can be seen from Figure 3, it is assumed that the onium compounds inhibit the cyclization of geranylgeranyl pyrophosphate to copalyl pyrophosphate (7), whereas it has been demonstrated in cell-free systems that pyrimidines, norbornenodiazetines, and triazoles inhibit the sequential oxidation of ent-kaurene to ent-kaurenoic acid (fj, 9). 

Aach, H., Bode, H., Robinson, D.G. and Graebe, J.E. (1997) Ent-kaurene synthase is located in proplastids of meristematic shoot tissues. Planta, 202, 211-9. 

Sun, T.-P. and Kamiya, Y. (1994) The Arabidopsis GAl locus encodes the cyclase ent-kaurene synthetase A of gibberellin biosynthesis. Plant Cell, 6, 1509-18. 

Yamaguchi, S., Saito, T., Abe, H., Yamane, H., Murofushi, N. and Kamiya, Y. (1996) Molecular cloning and characterization of a cDNA encoding the gibberellin biosynthetic enzyme ent-kaurene synthase B from pumpkin (Cucurbita maxima L). Plant., 10, 203-13. 

Yamaguchi, S., Sun, T.P., Kawaide, H. and Kamiya, Y. (1998) The ga2 locus of Arabidopsis thaliana encodes ent-kaurene synthase of gibberellin biosynthesis. Plant Physiol, 116,127-78. 

Full details have appeared of the incorporation of [2i - H,2- C,31 ]-, [2S- H,2- C,3i ]-, and [2- C,3/ ,5R- H]-mevalonic acids into kaurene (57), kaurenolides, and gibberellic acids. When [1- H2,2- C]- or [1- H2,1- C]-geraniol was used the radioactivity was retained in ent-kaurene (57), presumably with tritium at C-6. As expected, half of the tritium was lost with 7-hydroxy-ent-kaurenolide (60), 7,18-dihydroxy-cnt-kaurenolide (61), and gibberellic acid (63). However, Hanson has shown that gibbane aldehyde (62) retains all of the tritium, which means that in the ring contraction C-7 is oxidized and there is a hydrogen... 

Figure 21. Selected structures of ent-kaurenes found in various species of alpine lower and higher plants, and typical photooxidative reactions induced by moderate UV-vis light by photosensitizers.

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