1 -phenylethanol

Even though vanillin is produced on a large scale by chemical oxidation of lignin [61], up to now no practical applications of microbial processes has been demonstrated for this conversion. 

2-Phenylethanol (or 2-phenethyl alcohol) is an aromatic alcohol with a typical pleasant rose character, widely employed in cosmetics, perfumes, and food. Its odor is well perceived at 20 ppm and becomes undesirable in foodstuff at concentrations above 40 ppm [62]. 

Even though rose oil can contain more than 50% of this compound by weight, the process would not be cost effective because of the extremely high price of this starting material. De novo synthesis could certainly be an option in this case, since many microorganisms have been shown to produce 2-phenylethanol, but final concentrations are too low. 

Phenylethanol production is very strain-specific [65] and has been rarely observed in bacteria (Brevibacterium linens. Microbacterium sp.), while it is much more common in fungi. The best producers are doubtlessly the yeasts Kluyveromyces marxianus [66, 67] and Saccharomyces cerevisiae [68], but lower yields have been obtained with many strains, such as K. lactis [69], Pichia fermentans [70, 71], and P. (formerly//a/ise/i /a) anomala [72]. 

It is relevant to mention that the high-yield biotechnological production of 2-phenylethanol has been limited by its cytotoxic and antibacterial activity. Concentrations above 2.0 -4.0 g 1 slow down considerably or suppress the growth of many microorganisms [68, 73, 74]. 

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Wnte equations showing how 2 phenylethanol (CgH5CH2CH20H) could be prepared from each of the following starting materials... 

Benzyl alcohol (1) and P-phenethyl alcohol (2) (2-phenylethanol) are the simplest of the aromatic alcohols, and, as such, are chemically similar. Their physical properties are given in Table 1. 

Phenylethanol [60-12-8] M 122.2, b 215-217", d 1.020. Purified by shaking with a soln of ferrous sulfate, and the alcohol layer was washed with distd water and fractionally distd. 

Some alcohols that have been converted into the corresponding fluorides by reactions with diethyldminosulfur trifluoride include 1-octanol, 2-methyl-2-butanol, isobutyl alcohol, cyclooctanol, ethylene glycol, crotyl alcohol, 2-phenylethanol, 2-bromoethanol, ethyl lactate, and ethyl a-hydrox3maphthaleneacetate. ... 

Reactions of alcohols with sulfur tetrafluoride, because of decomposition and/or polymerization, usually do not give fluorinated products However, in the presence of a hydrogen fluoride scavenger like triethylamine or pyridine, even such sensitive substrates as benzylic alcohols [555], 2-phenylethanol, and 2-furylmethanol [554] can be fluorinated to give the expected fluoro derivatives (equation 73)... 

FIGURE 4.24 Adsorption chromatography of small molecules with a TSK-GEL G2500PWxl column. Column TSK-GEL G2500PWxl, 6 /tm, 7.8 mm X 30 cm. Sample (I) phenylacetic acid. (2) 3-phenylpropionic acid, (3) 4-phenylbutyric acid, (4) benzylamine, (5) 2-phenylethylamine, (6) 3-phenylpropylamine, (7) benzyl alcohol, (8) 2-phenylethanol, and (9) 3-phenyl-1 -propanol. Elution 0.1 M NaCIO, in water. Flow rate 2.0 ml/min. Temperature 65 C. Detection UV at 215 nm. 

Treatment of perhydropyrido[2,l-c][l,4]oxazine-3,6-dione 232 with B2H6 yielded (—)-(2i )-[(2S)-hydroxymethyl)piperldin-1 -yl]-2-phenylethanol (233) (00T233). Reduction of ( )-(3i ,4i ,9aS)-4-methyl-3-phenylperhydropyr-ido[2,l-c][l,4]oxazin-3-ol (234) with NaBH4 yielded ring-opened product 235 (97JHC1813). 

A single isomer of 4-phenylperhydropyrido[2,l-c][l,4]oxazin-l-one 319 was isolated from a reaction mixture of 2-bromocyclohexane and 2-azido-2-phenylethanol. The formation of 319 was deduced from azepino[l,2-i]... 

Hydrogenation of styrene oxide over palladium in methanol 66 gives exclusively 2-phenylethanol, but in buffered alkaline methanol the product is l-phenylelhanol. If alcoholysis of the epoxide by the product is troublesome, the problem can be eliminated by portion-wise addition of the epoxide to the reaction, so as always to maintain a high catalyst-to-substrate ratio. The technique is general for reactions in which the product can attack the starting material in competition with the hydrogenation. 

Problem 20.11 How might you prepare 2-phenylethanol from benzyl bromide More than one step is needed. 

Fig. 10.2 Structural formulae of alcohols used in preserving and disinfection A, 2-phenylethanol ...

Phenylethanol (phenylethy 1 alcohol 2-phenylethanol). Typical in-use concentration 0.25-0.5%. It is reported to have greater activity against Gram-negative organisms and is usually employed in conjunction with another agent. 

The presence of radical-stabilising groups can lead to C-C fission, for example in the V(V) oxidations of 2-phenylethanol and a-/ert-butylbenzyl alcohol, ... 

Although the 0-silylation reaction of the tertiary alcohol 1,1-dimethyl-2-phenylethanol (37) with 27 required a reaction temperature of 120 °C and two equivalents of 27, the 0-silyl ether 38 was still obtained in 86% yield by the simple solvent-free procedure. By contrast, the sterically hindered hydroxyl group of 37 was not silylated at all by heating with 27 in DMF at 120 °C for 5 h [8]. 

Hartmans S, JP Smits, MJ van der Werf, F Volkering, JAM de Bont (1989) Metabolism of styrene oxide and 2-phenylethanol in the styrene-degrading Xanthobacter strain 124X. Appl Environ Microbiol 55 2850-2855. 

The secondary benzylic alcohol l-phenylethan-l,2-diol requires 20 hours of treatment at room temperature to produce a 64% yield of 2-phenylethanol (Eq. 43).137 Under the same conditions, methyl mandelate fails to undergo reduction, presumably because of the greater carbocation-destabilizing effect of a neighboring carboalkoxy compared to a hydroxymethyl group (Eq. 43).137... 

The complex [Rh(COD)L L2]+, where L1 = PPh3 and L2 = pyridine, and a neutral benzoate complex, Rh(COD)(PPh3)(OCOPh), also effect highly selective hydrogenation of 1-alkynes to 1-alkenes as well as reduction of 1-alkenes and ketones to alcohols (139) the one equivalent of base required may be related to monohydride formation [Eq. (25)]. The bisphosphine complexes also catalyze reduction of styrene oxide to 2-phenylethanol and phenylacetaldehyde (140) ... 

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