5- levulinate esters

Under acidic conditions, furfuryl alcohol polymerizes to black polymers, which eventually become crosslinked and insoluble in the reaction medium. The reaction can be very violent and extreme care must be taken when furfuryl alcohol is mixed with any strong Lewis acid or Brn nstad acid. Copolymer resins are formed with phenoHc compounds, formaldehyde and/or other aldehydes. In dilute aqueous acid, the predominant reaction is a ring opening hydrolysis to form levulinic acid [123-76-2] (52). In acidic alcohoHc media, levulinic esters are formed. The mechanism for this unusual reaction in which the hydroxymethyl group of furfuryl alcohol is converted to the terminal methyl group of levulinic acid has recendy been elucidated (53). 

Oxopentanoate (Levulinate) Ester ROCOCH2CH2COCH3, LevOR Formation... 

The degradation of furfuryl alcohol in acidified methanol has been more extensively studied than the aqueous reaction. The following compounds, in addition to the levulinic ester and several dimers and... 

Levulinic esters. Levulinic esters of sugars can also be prepared by Mukaiyama s method for esterification with 2-chloro-l-methylpyridinium iodide (8, 95-96). Deblocking of the ester group is possible with hydrazine hydrate (1 equivalent, 20°).1... 

Furan-2-methanols are cleaved to derivatives of levulinic ester by methanolic hydrogen chloride a mechanism involving the carbonium ion (375) has been proposed. Under similar conditions, a,(3- unsaturated carbonyl compounds of type (384) undergo a similar rearrangement, a reaction known as the Marckwald rearrangement, and afford keto esters of type (385), as shown in Scheme 105 in an example drawn from a synthesis of equilenin (70AJC547). 

The coupling protocols described in the two previous examples can be combined to allow for the synthesis of branched carbohydrates.19 The automated solid-phase synthesis of a tetrasaccharide is illustrated in Scheme 4. Both glycosyl phosphate and glycosyl imidate building blocks were used along with acetate and levulinate esters as temporary protecting groups. 

Levulinic acid Glucose, fructose, xylose 1,4-Pentanediol, 5-methyl-2-pyrrolidone, acrylic acid, diphenolic acid, methyl tetrahydofuran (MTHF), levulinate ester, succinic acid, jS-acetyl-acrylic acid, y-valero-lactone Bozell etal., 2000 Keenan etal., 2004 Werpy and Petersen, 2004 Chang etal., 2007... 

DDQ deprotects TBS ethers in certain circumstances.379 In the case of Moeno-mycin intermediate 204 1 [Scheme 4.204], simultaneous deprotection of both a trityl group and a TBS ether in the presence of a levulinate ester and an anomeric phenylthio acetal was accomplished with DDQ in wet acetonitrile at... 

Wong and co-workers developed an efficient orthogonal protection-deprotec-tion strategy aimed at the synthesis of pentasaccharide libraries based on the galactose derivative 349.1 [Scheme 4.M9].664 The levulinate ester, chloroacetate... 

For the use of levulinate esters in very demanding circumstances, see Chapter 7, Schemes 7.20 and 7.36,... 

Oxopentanoate (Levulinate) Ester (Lev OR) ROCOCH2CH2COCH3 The levulinate is less prone to migrate than the benzoate and acetate. ... 

The rehydration product of HMF, levulinic acid, is also regarded as a potential biomass derived organic compound [35, 39,40]. Levulinic acid could be utilized as feedstock for several large volume chemicals (Fig. 7), e.g., methyltetrahydrofuran and levulinate esters (fuel additives), delta-amino-levulinic acid (herbicide), and diphenohc acid (replacer for bisphenol A for polycarbonates). 

Levulinic esters. Alcohols can be protected as the levuhnates, readily prepared by reaction of the alcohol with the anhydride in pyridine at 25°. The protecting group can be removed by NaBH4, which selectively reduces carbonyl groups in the presence of ester groups. This reaction is usually quantitative. This... 

Lead fetraacetate-Trifluoroacetic acid, 317 Lead tefrakis(trifluoroacetate), 318 Lemieux-Rudlolf oxidation, 455 Levulinic acid, 354 Levulinic anhydride, 318-319 Levulinic esters, 318-319 Limonene, 535 Lindlar catalyst, 67, 319 Lithioacetonitrile, 34, 636 1-Lithiocyclopropyl bromides, 89... 

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