2- bromoalkanoic acids

This simple procedure constitutes a very convenient, low-cost, and efficient synthesis of cinnamic acids. For example, reaction of a 25% MeONa in MeOH solution containing dimethyl phosphite with chloroacetic acid and then with aryl aldehydes affords (/ )-cinnamic acids in the range of 54-89%. This procedure is also apphcable to the carboxyvinylation of aldehydes or ketones with 2-bromoalkanoic acids and diethyl phosphite using NaH in DME as the base/solvent system. One of the major advantages of the overall procedure is that it avoids the need lo synthesize precursor reagents. 

Diacetone-D-glucose has also served as auxiliary for synthesis of (S)-2-haloalk-anoic acids, 374. Silyl enol ethers 373 were brominated or chlorinated (NBS or NCS) with 75-96 % d.e., oxidative cleavage of the auxiliary then yielding the (S)-2-chloro- and (S)-2-bromoalkanoic acids (Scheme 59)." ... 

The lipo-amino acids are generally synthesized as racemic mixtures which are resolved into optically pure a-amino acids by chemical or enzymatic methods.113" 137 133 The synthesis is based on the alkylation of diethyl acetamidomalonate followed by hydrolysis and decarboxylation. 129 138 140 Also, 20% DMF has been used in the hydrolysis step, as it is suitable for industrial scale preparation. 138] Alternatively, lipidated a-amino acids are synthesized by reacting a-bromoalkanoic acid with ammonium hydroxide. 141 ... 

The efficiency of detergentless microemulsions in promoting the formation of macrocyllc lactones has been studied in our laboratoriesThe two most direct routes to the formation of large macrocyclic lactones are the acid "catalyzed esterification of ii)-hydroxyalkanoic acids and the cyclization of potassium salts of lo-bromoalkanoic acids. In both reactions a competitive pathway yields polymeric material and as a consequence high dilutions are employed with the attendant extended reaction times. 

Dai and co-workers [183] have reported a one-pot U-4CR followed by an intramolecular O-alkylation sequence starting from a 2-aminophenol in combination with an a-bromoalkanoic acid, an aromatic aldehyde and an isocyanide under controlled microwave irradiation. The U-4CR was carried out in MeOH and the resulting acyclic intermediate 131 was turned into the 3,4-dihydro-3-oxo-2/f-1,4-benzoxazines 132, without isolation, upon treatment with an aqueous solution of K2CO3 to promote the intramolecular 0-aUcylation in high yields (Scheme 102). 

Reaction with carboxylic acids. a-Bromoalkanoic acids are obtained from the parent acids on exposure to NBS-HjSO, in trifluoroacetic acid at 85°. On the other hand, enoic acids undergo the Hunsdiecker reaction, and a catalytic version has been developed. ... 

The aliphatic-aromatic diacid monomers were prepared from the reaction of bromoalkanoic acid methyl ester and p-hydroxy benzoic acid methyl ester. The polymers of carboxyphenoxy alkanoic add of n = 3, 5, and 7 methylenes were soluble in chlorinated hydrocarbons and melted at temperatures below 100 °C. Copolymers of these monomers melted at lower temperatures than the respective homopolymers. These polymers displayed zero-order hydrolytic degradation profile ranging from 2 to 10 weeks. Increasing the length of the alkanoic chain, decreased the degradation rate of the polymer (Fig. 3). 

Halogenated PHAs. Several halogenated PHAs were obtained when certain bacterial species (P. oleovorans, P. putida) were cultured in media containing chlorinated, brominated or fluorinated compounds. A copolyester containing (R)-3-hydroxyoctanoate, (P)-3-hydroxy-8-chlorooctanoate, (P)-3-hydroxyhexanoate and (/ )-3-hydroxy-6-chlorohexanoate was synthesized when a culture of P. oleovorans was fed with octane and 1-chlorooctane as carbon sources (Doi and Abe 1990). Additionally, PHAs containing brominated monomers were produced by P. oleovorans when it was cultured in media containing mixtures of n-alkanoic acids (octanoic and nonanoic acids) and co-bromoalkanoic acids (Kim et al. 1992). 

Table 2. Fermentation results from mixtures of w-bromoalkanoic acids and nonanoic acid...

Liberation of amines. A modification of the classical Gabriel synthesis to gain access to a-amino acids using chiral a-bromoalkanoic esters to react with potassium phthalimide catalyzed by a chiral phase transfer agent has been reported. Unfortunately, the results are not very satisfactory. 

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