Alcohols biosynthesis

Savidge, R. A. Forster, H. Coniferyl alcohol metabolism in conifers—II. Coniferyl alcohol and dihydroconiferyl alcohol biosynthesis. Phytochemistry 2001, 57, 1095-1103. 

Table II shows (28) a correlation between the biosynthesis of veratryl alcohol and PAL activities, both of which are affected by initial glucose and ammonium salt levels. The HC-LN culture with a C/N ratio of 240, which is almost comparable to that of wood, shows the greatest amount of veratryl alcohol biosynthesis and, therefore, the highest PAL activity. As can be seen, depending upon the C N balance of the media used, the amounts of secondary metabolites formed and PAL activites can vary greatly (Tables I and II).

Physiological and Biochemical Relationships between Lignin Biodegradation and Veratryl Alcohol Biosynthesis... 

Parallel physiological and biochemical relationships between lignin biodegradation and veratryl alcohol biosynthesis are summarized below ... 

The level of cyclic AMP (cAMP) is increased by nitrogen starvation this triggers expression of ligninolytic activity and veratryl alcohol biosynthesis (40). 

Harper D. B., Buswell J. A., Kennedy J. T., and Hamilton J. T. G. (1990) Chloromethane, methyl donor in veratryl alcohol biosynthesis in Phanerochaete chrysosporium and other lignin-degrading fungi. Appl. Environ. Microbiol. 56, 3450-3457. 

A COMPARISOH OF STEROL AND LONG CHAIN FATTY ALCOHOL BIOSYNTHESIS IN SORGHBM BICOLOR... 

The earliest references to cinnamic acid, cinnamaldehyde, and cinnamyl alcohol are associated with thek isolation and identification as odor-producing constituents in a variety of botanical extracts. It is now generally accepted that the aromatic amino acid L-phenylalanine [63-91-2] a primary end product of the Shikimic Acid Pathway, is the precursor for the biosynthesis of these phenylpropanoids in higher plants (1,2). 

The first step in the biosynthesis of eicosanoids from arachidonic acid is generally a lipoxygenation reaction. The resulting hydroperoxides (HPETE s) can undergo reduction to the corresponding alcohols (HETE s). Preparative routes to the 5-, 11-, and 15-HETE s and HPETE s have been developed as oudine below. 

Long-chain polyisoprenoid. molecules with a terminal alcohol moiety are called, polyprenols. The dolichols, one class of polyprenols (Figure 8.18), consist of 16 to 22 isoprene units and, in the form of dolichyl phosphates, function to carry carbohydrate units in the biosynthesis of glycoproteins in animals. Polyprenyl groups serve to anchor certain proteins to biological membranes (discussed in Chapter 9). 

The next three steps—reduction of the /3-carbonyl group to form a /3-alcohol, followed by dehydration and reduction to saturate the chain (Figure 25.7) — look very similar to the fatty acid degradation pathway in reverse. However, there are two crucial differences between fatty acid biosynthesis and fatty acid oxidation (besides the fact that different enzymes are involved) First, the alcohol formed in the first step has the D configuration rather than the L form seen in catabolism, and, second, the reducing coenzyme is NADPH, although NAD and FAD are the oxidants in the catabolic pathway. 

In biological pathways, dehydrations rarely occur with isolated alcohols but instead normally take place on substrates in which the -OH is positioned two carbons away from a carbonyl group. In the biosynthesis of fats, for instance, /3-hydroxybutyry) ACP is converted by dehydration to tram-crotonyl ACP, where ACP is an abbreviation for acyl carrier protein. We ll see the reason for this requirement in Section 11.10. 

Two SN1 reactions occur during the biosynthesis of geraniol, a fragrant alcohol found in roses and used in perfumery. Geraniol biosynthesis begins with dissociation of dimethylallyl diphosphate to give an allylic carbocation, which reacts with isopentenyl diphosphate (Figure IT 15). From the viewpoint of isopentenyl diphosphate, the reaction is an electrophilic alkene addition, but from tile viewpoint of dimethylallyl diphosphate, the process in an Sjjl reaction in which the carbocation intermediate reacts with a double bond as the nucleophile. 

All three elimination reactions--E2, El, and ElcB—occur in biological pathways, but the ElcB mechanism is particularly common. The substrate is usually an alcohol, and the H atom removed is usually adjacent to a carbonyl group, just as in laboratory reactions. Thus, 3-hydroxy carbonyl compounds are frequently converted to unsaturated carbonyl compounds by elimination reactions. A typical example occurs during the biosynthesis of fats when a 3-hydroxybutyryl thioester is dehydrated to the corresponding unsaturated (crotonyl) thioester. The base in this reaction is a histidine amino acid in the enzyme, and loss of the OH group is assisted by simultaneous protonation. 

In step 6 of fatty-acid biosynthesis (Figure 29.5), acetoacetyl A CP is reduced steieospecifically by NADPH to yield an alcohol. Does hydride ion add to the Si face or the Re face of acetoacetyl ACP ... 

Indolmycin, biosynthesis of, 864 Inductive effect. 37, 562 alcohol acidity and. 604 carboxylic acid strength and. 758 electronegativity and, 37 electrophilic aromatic substitution and, 562... 

Quinone methides have been shown to be important intermediates in chemical synthesis,1 2 in lignin biosynthesis,3 and in the activity of antitumor and antibiotic agents.4 They react with many biologically relevant nucleophiles including alcohols,1 thiols,5-7 nucleic acids,8-10 proteins,6 11 and phosphodiesters.12 The reaction of nucleophiles with ortho- and /iara-quinone methides is pH dependent and can occur via either acid-catalyzed or uncatalyzed pathways.13-17 The electron transfer chemistry that is typical of the related quinones does not appear to play a role in the nucleophilic reactivity of QMs.18... 

---