Abscisic aldehyde

a new synthesis, isotopic labelling, exchange reactions and oxidation

R. D. Willows, B. V. Milborrow*

*Corresponding author for this work

Research output: Contribution to journalArticle

7 Citations (Scopus)

Abstract

Abscisic aldehyde (AB-ald) has been synthesized from (±)-R-S-1′-hydroxy,4′-oxo-α-ionone by a novel route (using a silyl ylid) that allows the ready incorporation of isotopes of C and H. SIM-NICI GC-MS of such labelled materials provides a sensitive and accurate method of measurement. AB-ald reacts with pentafluorobenzyl hydroxylamine to form a pentaflurobenzyl-oxime at C-1 and also at C-4′ under basic conditions. These derivatives improve the sensitivity of detection by GC by ca five-fold in comparison with the underivatized compound. AB-ald exchanges its C-1 oxygen atom with the medium in basic (pH 8.5 t1/2 < 3 min) and acidic (pH 3 t1/2 < 3 min) conditions with a minimum at ca pH 5.5 (t1/2 = 50 min). Loss of 18O from C-1 of AB-ald may distort apparent 18O incorporation values into ABA obtained in biosynthetic experiments using 18O2. Tomato shoots oxidized (±)-RS-AB-ald and (±)-RS-2-trans-AB-ald to ABA and 2-trans-ABA, respectively. When (+)- [6-2H3] AB-ald was supplied and the ABA resolved as MeABA in a Chiralcel HPLC column, both (+)-S and (-)-R ABA were labelled but the (+) enantiomer predominated (ca 2:1). AB-ald in aqueous solutions was slowly oxidized in air to ABA (16%) and other products (84%) and some of the ABA in the tomato shoots, therefore, may have been formed non-enzymically. It was also noted that when dilute solutions of AB-ald (0.1-10,μg ml-1) were exposed to air the 2-cis isomer was oxidized more rapidly than the 2-trans isomer with a concomitant change in the apparent ratios of the two isomers of AB-ald.

Original languageEnglish
Pages (from-to)2649-2653
Number of pages5
JournalPhytochemistry
Volume31
Issue number8
DOIs
Publication statusPublished - 1992
Externally publishedYes

Keywords

  • (+) and (-) enantiomers.
  • abscisic acid
  • Abscisic aldehyde
  • deuteriation
  • internal standards
  • isomerization
  • MS

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