Dibenzoyl tartrate

Table 5-1. Enantioselectivities determined for several drugs. All experiments were performed at room temperature, except those marked with, which were performed at 4 °C. In some cases a lipophilic anion was used to facilitate the solubilization of the drug in the organic phases (PFj = hexafluorophosphate BPh = tetraphenyl borate). DHT = dihexyl tartrate DBT = dibenzoyl tartrate PLA = poly (lactic acid). ...

S)-N-(tert-butoxycarbonyl)-hydroxymethylpiperidine (8) is a key intermediate in the synthesis of a potent tryptase inhibitor (Scheme 7.5). It was synthesized from (R,.S)-3-hydroxyrnethylpiperidine via fractional crystallization of the corresponding L(-)dibenzoyl tartrate salt followed by hydrolysis and acylation [17]. The lipase from Pseudomonas cepacia (PS-30) immobilized on polypropylene accurel PP catalyzed the esterification of racemic 6 with succinic anhydride and toluene, giving the (S)-hemisuccinate ester (7). This was easily separated and hydrolyzed by base to the (S)-Boc-protected 3-hydroxymethylpiperidine (8). Using this repeated esterification procedure gave a 32% yield (maximum theoretical yield = 50%) and 98.9% . 

Anatoxin-a (3) is a powerful neurotoxin (inhibitor of acetylcholine esterase) found in freshwater blue-green algae. The compound was required as an analytical standard and also for development of an immunoassay. It was synthesized by the 8-step sequence summarized in Scheme 29.1. The key intermediate 4 was resolved by separation of the dibenzoyl tartrates, and the remaining steps then gave both (+)- and (-)-anatoxin-a.2 The efficiency of the resolution was monitored by formation of the BocAla derivatives, which were distinguishable by NMR an ee of >98% was achieved even before recrystallization of the salts. It is also noteworthy that the published absolute configuration of the intermediate 53 was shown to be in error by X-ray crystallography. 

A classical resolution using dibenzoyl tartrate affords an even simpler synthesis of the chiral phenyl glycine intermediate 35. 

With morphinan 20 in hand, the stage was set for the deracemization and functionalization of the D ring of the alkaloid. Resolution of racemic amine 20 with dibenzoyl tartrate (Scheme 2) afforded the isomer with correct configuration at C9 and Cl3 but epimeric at Cl4. The identity of the synthetic material was unambiguously confirmed... 

The second type of diastereomer comprises those salts where both the anionic and cationic parts are chiral. The nature of the chiral elements involved here can be variable for example, a cation (2.16) with C2 symmetry and an anion containing asymmetric carbon atoms such as dibenzoyl tartrate (2.30), a cation relevant to planar chirality (2.31) with an anion (2.32) of D3 symmetry,or finally an anion (2.32) and a cation (2.17) both of D3 symmetry.These three examples are shown in Figure 2.34. 

Bis(binaphthylamine) Ugand 7, developed by Cram, is synthesised by the cou-pUng of two equivalents of 2,2 -bis(bromomethyl)-1,1 -dinaphthyl with 1,2-di-aminoethane, a subsequent (-)-dibenzoyl tartrate resolution affording both enantiomers of 7. As with Mukaiyama s system, the use of other organolithiiuns in the addition gave only moderate levels of ee. 

Fig. 16 Sensors used in enantioselective aggregation induced enhancement (a) Phenylglycinol-derived Schiff base 52 (b) proposed mechanism of oligomeric interaction of 52 with mandelic acid enantiomers (c) chiral derivatives of 2-phenyl-3-(p-ammophenyl)acrylonitrile 53,54 showing an AIEE effect in the presence of bases and acids respectively (d) fluorescence response as a function of enantiomeric excess of dibenzoyl tartrate observed using the amine 54 (adapted from [113]. Copyright (2010) with permission from Elsevier) (e) AIEE sensor 55, based on BINOL...

Qin H, He Y, Hu C et al (2007) Enantioselective fluorescent scmsm Iot dibenzoyl tartrate anion based rm chiral binaphthyl derivatives bearing an amino acid unit. Tetrahedron Asymmetry 18 1769-1774... 

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