Ethyl n-Pentanoate

Ethyl N-benzylcarbamate, 35, 91 Ethyl 3-benzyl 2 cyano 3 methyl-pentanoate, 35, 7 Ethyl bromide, 34, 58, 36, 87 Ethyl a-bromobutyrate, 37, 44 Ethyl a bromopropionate, 35, 17, 37, 38... 

Although irinotecan metabolism generates at least 20 metabolites, many of them are found at trace levels in patients. Clinically relevant metabolites of irinotecan are the active metabolite 7-ethyl-10-hydroxycamptothecin (SN-38), inactive glucuro-nide SN-38G, and inactive aminopentane carboxylic acid (7-ethyl-10[4-N-(5-amino-pentanoic acid)-l-piperidino]carbonyloxycamptothecin, APC) (Figure 14.5). 

The ethyl sec,-butylmalonate was prepared from sec-butyl bromide and malonic ester according to the general method described in Org. Syn. 4, n. The yield of ester boiling at i24-i32°/28 mm. was 80-81 per cent of the theoretical amount. The yields of 3-methyl pentanoic acid given in this procedure were obtained with this grade of ester. 

Hydroxy-6-methoxybenzaldehyde (16.875 g, 0.111 M), ethyl 5-bromopentanoate (23.25 g, 17.6 ml, 0.111 M), anhydrous potassium carbonate (16.5 g), sodium iodide (0.675 g) and 95% ethanol (150 ml) were refluxed with stirring (16 hours). The cooled reaction mixture was filtered and the solid washed well with ethanol. The filtrate was evaporated to dryness and the residue partitioned between ether and water. The ethereal layer was separated and washed with 2 N sodium hydroxide solution, water, dried (sodium sulfate) and evaporated. The residue was dissolved in 95% ethanol (300 ml) and 0.66 N sodium hydroxide solution (450 ml) and stirred at ambient temperature (4 hours). The reaction mixture was evaporated to half volume and diluted with water. The mixture was extracted once with ether and the aqueous layer acidified with concentrated hydrochloric acid with cooling. The crystalline solid formed was filtered off and washed well with water. Recrystallisation from ethyl acetate-petrol gave 5-(2-formyl-3-methoxyphenoxy)pentanoic acid, melting point 99-101°C. 

A mixture of ethyl 5-(2-formyl-3-benzyloxyphenoxy)pentanoate (3.61 g, 0.01 M), potassium hydroxide (1.19 g, 0.021 M) and ethanol (40 ml) were stirred at 50°-60°C for 5 hours. The ethanol was then removed in vacuum, the residue dissolved in water (50 ml) and the solution extracted with ether (2 x 80 ml). The aqueous layer was then acidified by the addition of 2 N aqueous hydrochloric acid and the product extracted with ether, and the combined extracts washed with water to neutrality, dried, and concentrated in vacuum to give 5-(2-formyl-3-benzyloxyphenoxy)pentanoic acid, 3.0 g, 91% as a yellow oil which crystallized on standing. The crude solid was crystallized from benzene/petroleum ether to give pale cream crystals, melting point 110°C. 

AI3-33618 EINECS 254-384-1 Ethyl 2-methylpentanoate Ethyl 2-methyivalerate Ethyl a-methylvalerate FEMA No. 3488 Pentanoic acid, 2-methyl-, ethyl ester. Oil with a natural, fruity, pineapple odor. Used in specialty perfumes and fruit flavorings. Oil bpi5 = 60" d n 0.861-0.865. Quest Inti. 

Acetonitrile Anthranilic acid Benzoyl chloride 2-t-Butylphenol p-t-Butyl toluene Camphene Decene-1 Ethyl chloride 1-Hexene Isobutylbenzene 4-Methyl pentanoic acid p-Pinene n-Valeric acid... 

The basic product of the reaction is 2-methyl-butane-3-one (methylisopropyl ketone) in the absence of water, whereas pivalic acid represents the basic product in the presence of water at 70°C and 8 atm partial CO pressure. Conversion of alkane (36%) was reached at 1 h of the reaction time vmder conditions of batch reactor (81). Under similar conditions n-pentane converts into a mixture of Ce-aldehydes [2-ethyl-butyraldehyde (5%), 2-methyl-pentanaldehyde (3%)] and ketones [2-methyl-pentane-3-one (11%) and 3-methyl-pentane-2-one (5%)] at 24% total conversion of n-pentane (82). In the presence of water n-pentane gives a mixture of three acids 2-ethyl-butjrric acid, 2-methyl-pentanoic acid, and 2,2-dimethyl-butyric acid at 150-200°C, 10 atm CO pressure, and 20% total n-pentane conversion. Carbonylation of propane gives rise to a mixture of isobutyric acid and isobutyraldehyde at 150°C, 10 atm CO pressure, and 22% propane conversion, isobutyric acid being the main product. 

Typical procedure. tert-Butyl 2-isocyano-4-methyl pentanoate 1554 [1182] N-Formyl-leucine tert-butyl ester 1553 (5.00 g, 23.2 mmol) and triethylamine (7.13 g, 69.7 mmol) were dissolved in dichloromethane (36 mL) and the solution was cooled to 0 °C. At this temperature, a solution of triphosgene (2.30 g, 7.74 mmol) in dichloromethane (25 mL) was added dropwise. The mixture was stirred for 2 h at room temperature, water (5 mL) was then poured into it, and the phases were separated. The organic layer was washed with 5% aq. sodium hydrogen carbonate solution, dried over sodium sulfate, and concentrated in vacuo. The residue was chromatographed on silica gel eluting with ethyl acetate to furnish tert-butyl 2-isocyano-4-methyl pentanoate 1554 (4.29 g, 94%) as a colorless oil. 

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