- Biosynthesis of steroidal alkaloids in Solanaceae plants: Involvement of an aldehyde intermediate during C-26 amination
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The C-26 amino group of steroidal alkaloids, such as tomatine, is introduced during an early step of their biosynthesis from cholesterol. In the present study, the mechanism of C-26 amination was reinvestigated by administering stable isotope labeled compounds, such as (26,26,26,27,27,27- 2H6)cholesterol during biosynthesis of tomatine, solanine and solasonine. The chemical compositions of tomatine and solanine so obtained were analyzed by LC-MS after administering the d6-cholesterol to a tomato seedling and a potato shoot, respectively. The resulting spectra indicated that two deuterium atoms were eliminated from C-26 of cholesterol during biosynthesis. Furthermore, administration of (6-13C 2H3)mevalonate in combination with lovastatin to an eggplant seedling, followed by GC-MS analysis of solasodine after TMS derivatization established that two deuterium atoms were eliminated from C-26 of cholesterol during solasonine biosynthesis. These findings are in contrast to an earlier observation that one hydrogen atom was lost from C-26 during tomatidine biosynthesis, and suggest that C-26 nitrogen atom addition involves an aldehyde intermediate. Thus, it is proposed that the C-26 amination reaction that occurs during steroidal alkaloid biosynthesis proceeds by way of a transamination mechanism.
- Ohyama, Kiyoshi,Okawa, Akiko,Moriuchi, Yuka,Fujimoto, Yoshinori
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- Synthesis of Cholesterol and Derivatives substituted in the Side chain
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The carbanion derived from 24-phenylsulphonylchol-5-en-3β-ol 3-tetrahydropyranyl ether (6) reacted with acetone to give the 24-phenylsulphonyl-25-hydroxycholesterol derivative (7a), which was reduced by sodium amalgam to a separable mixture of the labelled 25-hydroxycholesterol and cholest-5,24-dien-3β-ol (desmosterol) derivatives. Cholesterol has been obtained via a selective reduction of the Δ24-unsaturation in desmosteryl benzoate with di-imide, or more efficiently by reducing 25-hydroxycholesteryl 3,25-diacetate w ith litium in ethylamine, without significant loss of label.The labelled 24,25-dihydroxycholesterols were also prepared from desmosteryl benzoate.
- Kirk, David N.,Varley, Michael J.,Makin, Hugh L.J.,Trafford, David J.H.
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p. 2563 - 2567
(2007/10/02)
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