Biosynthesis of isoprenic units via different pathways: Occurrence and future prospects

Biosynthetic origins of the isoprene units of 4-nerolidylcatechol in Potomorphe umbellata

“…Specific and/or non-specific incorporations of ≥ 1% were obtained within 72 h of feeding with [3-14 C]-R,S-mevalonolactone and [U-14 C]-glyceraldehyde-3-phosphate but, as would be expected, a considerably lower percentage incorporation (0.1 -0.3%) was attained with [U-14 C]-glucose. In order to determine the specificity of incorporation, and hence the possible biosynthetic origin of the isoprenoid moieties, experiments involving the incorporation of [1][2][3][4][5][6][7][8][9][10][11][12][13] C]-glucose into 4-nerolidylcatechol (1) were carried out. Different patterns of 13 C-enrichment in 1 would be expected depending on the pathway followed.…”

“…10,13,14 Thus, the conversion of [1-13 C]-glucose into IPP via the MVA pathway would lead to the incorporation of label at positions 2, 4 and 5 of each isoprene unit. On the other hand, if [1][2][3][4][5][6][7][8][9][10][11][12][13] C]-glucose is converted into pyruvate, the resulting C 5 units derived from the triose/pyruvate pathway should be labelled at positions 1 and 5 ( Figure 1). Whichever of the two pathways is extant, no label should appear at position 3 of any of the isoprene units if [1-13 C]-glucose is specifically incorporated into 1.…”

“…In feeding experiments involving [1][2][3][4][5][6][7][8][9][10][11][12][13] C]-glucose as a putative precursor, eight young leaves of P. umbellata were fed for 72 h with 100 μL of a 10% solution of [1][2][3][4][5][6][7][8][9][10][11][12][13] C]-glucose, and then extracted with ethanol. The ethyl acetate soluble portion of the ethanol extract was fractioned by column chromatography over silica gel followed by TLC to afford 4-nerolidylcatechol (1).…”

“…However, an alternative pathway has been shown to be involved in the formation of the hopane triterpenes in bacteria 3 and, more recently, the widespread occurrence of this route within the plant kingdom has been demonstrated. [4][5][6][7][8] The reaction sequence of the alternative pathway involves condensation of pyruvate and glyceraldehyde-3-phosphate leading to the formation of 1-desoxyxylulose-5-phosphate, the first C 5 intermediate. Several subsequent steps, including an intramolecular rearrangement, lead to IPP.…”

Minor Labdane Diterpenes from Marrubium thessalum

“…CH 2 (11) and CH 2 (12) were located in the spiro ring that is located between the central skeleton and the spiro-lactone ring. The two AB systems in H-NMR spectrum was attributed to HÀC (15), which corresponded to a doubly Obearing C-atom. The presence of a MeO group in the structure was easily recognized in the 1 H-NMR spectrum, and this MeO group was at C(15), based on the correlations in the HMBC spectrum (MeO/C(15)).…”