- A refined method for the removal of the methoxymethyl (MOM) protecting group for carbinols with acidic ion-exchange resin
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The methoxymethyl protecting group for carbinols is best removed from acid-sensitive substrates by hydrolysis in aqueous methanol using a cationic exchange resin (Dowex-50W).
- Seto,Mander
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p. 2823 - 2828
(2007/10/02)
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- Effects of 3-Methylgibberellin Analogs on Gibberellin 3&β-Hydroxylases and Plant Growth
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Six 3-methylgibberellin analogs were synthesized, and their effects on the GA 3β-hydroxylases from immature seeds of Phaseolus vulgaris and Cucurbita maxima, and/or on the growth of dwarf rice (Oryza sativa L. cv.Tan-ginbozu) and cucumber (Cucumis sativus L. cv.Spacemaster) were investigated. 3-Methyl-GA5 and 2,3-didehydro-3-methyl-GA9 inhibited the conversion of GA9 to GA4 by GA 3β-hydroxylases from both P. vulgaris and C. maxima at 3 μM and higher.Their C/D-ring-rearranged isomers, 2,3-didehydro-3-methyl-DGC and 16-deoxo-2,3-didehydro-3-methyl-DGC, inhibited 3β-hydroxylation by the enzyme from P. vulgaris threefold more strongly than the non-C/D-ring-rearranged compounds, but exhibited no effect on 3β-hydroxylation by the enzyme from C. maxima.In a dwarf rice seedling assay, 3-methyl-GA5 and 2,3-didehydro-3-methyl-GA9 promoted shoot elongation at doses of 300 ng/plant and higher, and 3α-methyl-GA1 and 3α-methyl GA4 at doses of 30 ng/plant and higher.In contrast 2,3-didehydro-3-methyl-DGC inhibited shoot growth to half that of the control at a dose of 300 ng/plant, and 16-deoxo-2,3-didehydro-3-methyl-DGC showed no effect on growth.In a cucumber seedling assay, 3α-methyl-GA4 promoted hypocotyl elongation at doses of 300 ng/plant and higher.The other C-3 methyl compounds showed no effect on the hypocotyl elongation of cucumber seedlings.
- Saito, Tamio,Kamiya, Yuji,Yamane, Hisakazu,Sakurai, Akira,Murofushi, Noboru,Takahashi, Nobutaka
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p. 1046 - 1052
(2007/10/02)
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- METHYLENATION OF CARBONYL COMPOUNDS WITH Zn-CH2Br2-TiCl4.APPLICATIONS TO GIBBERELLINS
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A highly active species prepared from Zn-CH2Br2-TiCl4 reacted instantaneously with aldehydes and ketones to give methylenated products with exceptional selectivity.
- Lombardo, Luciano
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p. 4293 - 4296
(2007/10/02)
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- Preparation of Gibberellins A9 and A20 from Gibberellic Acid
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Methyl gibberellate has been converted via the methyl ester of 3-epigibberellin A1 into the 3β-chloro- and 3β,13-dichloro-derivatives using triphenylphosphine and carbon tetrachloride.Hydrogenolysis of the chlorides with tributyltin hydride afforded gibberellins A20 and A9 as their methyl esters.Gibberellin A9 methyl ester was also prepared from the gibberellin A4/A7 mixture.The stereochemistry of the conjugate reduction of the ring-A-unsaturated ketone is defined.
- Duri, Zvitendo J.,Fraga, Braulio M.,Hanson, James R.
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p. 161 - 164
(2007/10/02)
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