Isoleucin Hydrochlorid

For crystallization by acid addition, the effects of acid addition rate, agitation, and initial solution composition were examined. The experiments had constant initial and final temperatures, although there were some variations in temperature during a run because of the heat of crystallization of L-isoleucine hydrochloride (L-Ile HCl H20) and heat of solution of acid. The acid used was in the form of 37% HCl. The initial conditions of the batch corresponded to an HCl concentration giving the maximum solubility of L-Ile (1). A schematic of the batch crystallizer is shown in Figure 3. 

The iminium salt 132, generated from benzylamine hydrochloride and aqueous formaldehyde, reacts with cyclopentadiene during 3 h at room temperature to give, after basification, the cycloadduct 133 in nearly quantitative yield (equation 70). Other examples of this reaction are shown in equations 71-75. The separable diastereomers 134 and 135 are formed in the ratio 4 1 from cyclopentadiene, (—)-a-methylbenzylamine hydrochloride and aqueous formaldehyde in a combined yield of 86% (equation 75)62. Hydrochlorides 136 of methyl esters of natural amino acids [(S )-valine, (S )-isoleucine] react with cyclopentadiene and formaldehyde in aqueous THF to produce mixtures of the diastereomers 137 and 138, in which the former predominate (equation 76)63. 

The compounds investigated were the amino acids L-isoleucine, L-leucine, L-valine, and L-a-amino butyric acid. These compounds have similar molecular structures, as shown in Figure 2, and will be referred to throughout the present work as L-Ile, L-Leu, L-Val, and L-a-ABA. Where there is little likelihood of confusion, the designation L- will be omitted. Operations examined included crystallization of He through the addition of hydrochloric acid and through cooling. Under acidic conditions He crystallizes as a hydrochloride salt while in the vicinity of the isoelectric point (pH 5.2) it crystallizes as the neutral zwitterionic... 

Trommel, J., and Bijvoet, J. M. Crystal structure and absolute configuration of the hydrochloride and hydrobromide of D(-)-isoleucine. Acta Cryst. 7, 703-709 (1954). 

Asymmetric induction occurs when (S)-l-phenylethylamine hydrochloride is used as the ammonium salt [57], which prompted Waldmann to investigate amino acid methyl esters as chiral auxiliaries the reaction of (S)-isoleucine methyl ester with cyclopentadiene in the presence of 35% aqueous formaldehyde solu-tion/tetrahydrofuran (9 1) afforded the best stereoisomeric ratio (93 7) [62],... 

A series of various enantiomerically pure amino acid ester isocyanates (for example 452) has been synthesized in yields of 72-95% by carbonylation of the appropriate amino acid ester hydrochlorides (for example 451) with phosgene [311]. The products are based on the amino acids alanine, valine, leucine, isoleucine, phenylalanine, methionine, serine, and glutamic acid. 

L-Cysteinyl-L cysteine monohydrate, 43B, 596 L-Cystine (hexagonal form), 23, 593 L-Cystine (tetragonal form), 40B, 439 imonium DL-7-carboxyglutamate, 45B, 512 L-Alanyl-L-alanine hydrochloride, 34B, 270 lloisoleucine, 41B, 531 Isoleucine, 39B, 352 Leucine, 41B, 530 Norleucine, 17, 659 isoleucune, 37B, 268 Leucine, 42B, 355 leucine, 39B, 349... 

Waldman et al. [7] extended and improved the asymmetric methodology by utilizing (/ )- and (.S)-amino acid ester hydrochlorides as chiral auxiliaries in analogous aza Diels-Alder processes. A variety of chiral amino acids were evaluated, with isoleucine providing the best asymmetric induction. A typical protocol involves reacting (iS)-isoleucine methyl ester hydrochloride with aqueous formaldehyde in the presence of the diene in water-tetrahydrofuran (11/1) at 0°C. Use of cyclopentadiene provides the corresponding azanor-bomene products, 16 and 17, in excellent stereoisomeric ratio (93/7) in 57% yield (Scheme 2.1). In the case of the less-reactive cyclohexadiene, the corresponding diastereomers are formed at 25 C in a 80/20 ratio in 35% yield. 

---