- Probing the mechanism of loss of carbon-20 in gibberellin biosynthesis. Synthesis of gibberellin 3α,20-hemiacetal and 19,20-lactol analogues and their metabolism by a recombinant GA 20-oxidase
-
A gibberellin 3α,20-hemiacetal,1 (equivalent to 3-epi-gibberellin A36), has been synthesised from gibberellin A13. Turnover of this hemiacetal by recombinant gibberellin 20-oxidase occurred with loss of the 20-carbon atom to give the 20-nor-19,10-lactone (3-epi-gibberellin A4). In addition, two other enzyme products were detected and identified by synthesis as 3-epi-20-norgibberellin A13 and 3-epi-1,10-didehydro-20-norgibberellin A13. These by-products indicate that the enzymatic reaction proceeds via a C-10 radical intermediate. Carbon radicals at C-10 and acyl radicals at C-20 were generated chemically and their decomposition products were studied with reference to the biological mechanism. The corresponding 19-nor-3α,20-hemiacetal 3 and 19-methylene analogue 4 were synthesised but were not oxidised at C-20 by the enzyme. These results indicate that the 19-carboxylic acid is an essential component of the enzyme reaction.
- Ward, Jane L.,Gaskin, Paul,Brown, Robert G. S.,Jackson, Graham S.,Hedden, Peter,Phillips, Andy L.,Willis, Christine L.,Beale, Michael H.
-
p. 232 - 241
(2007/10/03)
-
- METHYLENATION OF CARBONYL COMPOUNDS WITH Zn-CH2Br2-TiCl4.APPLICATIONS TO GIBBERELLINS
-
A highly active species prepared from Zn-CH2Br2-TiCl4 reacted instantaneously with aldehydes and ketones to give methylenated products with exceptional selectivity.
- Lombardo, Luciano
-
p. 4293 - 4296
(2007/10/02)
-
- PREPARATION OF 2- AND 3-SUBSTITUTED GIBBERELLINS A9 AND A4 FOR BIOASSAY
-
Key Word Index - Partial synthesis; 2α,2β- and 3β-derivatives; gibberellin A4; gibberellin A9. To test the effects of preventing enzymatic 2β- and 3β-hydroxylation on the biological activities of gibberellins, the preparation of the following compounds is described: 2β-methyl- and 2,2-dimethyl-gibberellins A4 and A9; 2α-fluoro-, 2β-fluoro- and 2β-methoxy-gibberellin A9; and 3β-fluoro, 3β-methoxy-and 3-methylene A9.
- Beale, Michael H.,Macmillan, Jake
-
p. 693 - 702
(2007/10/02)
-
- STEREOSELECTIVE REDUCTION OF 3-KETO GIBBERELLIN ACIDS TO 3β-OLS USING K-SELECTRIDE WITH KH2PO4 BUFFER
-
KH2PO4 buffered K-Selectride gives with 3-keto gibberellin acids, borates which are reduced stereoselectively to 3β-ols.
- Bell, Russell A.,Turner, John V.
-
p. 4871 - 4872
(2007/10/02)
-
- TOTAL SYNTHESIS OF GIBBERELLIN A4
-
A general approach to the preparation of 13-deoxy C19 gibberellins has been established with the total synthesis of (+/-)gibberellin A4 (3).
- Cossey, Ailsa L.,Lombardo, Luciano,Mander, Lewis N.
-
p. 4383 - 4386
(2007/10/02)
-
