Chiral tartaric amides

Further work on the preparation of chiral a-amino-acids reported in the past year (see also the section on asymmetric hydrogenation) includes an extension of the utility of anions derived from lactim ethers (228) in the synthesis of such compounds by condensations with aldehydes and ketones chiral inductions are somewhat lower than in the alkylations of (228) reported previously (4, 320). Enzyme-mediated hydrolysis of 5(4H)-oxazolones by chymotrypsin or subtilisin gives a-acylamino-acids with good enantiomeric enrichments, especially if the substrate carries bulky substituents. Schiff s bases of a-amino-esters can be enriched enantiomerically to an extent of up to 70% by sequential deprotonation with a chiral lithium amide and protonation with an optically pure tartaric acid. ... 

The directive effect of allylic hydroxy groups can be used in conjunction with chiral catalysts to achieve enantioselective cyclopropanation. The chiral ligand used is a boronate ester derived from the (VjA jA N -tetramethyl amide of tartaric acid.186 Similar results are obtained using the potassium alkoxide, again indicating the Lewis base character of the directive effect. 

Among the different types of compounds whose complexation properties have been studied are various amides linear oxoamide 9 [22], fumaramide 10 [23,24] and methanetricarboxamide 11 [25], biphenyl derivatives 12 [26], and derivatives of tartaric acid 13-16, that can also be prepared in an optically active form [27], The above-mentioned chiral hosts have been found to form inclusion complexes with chiral guests 17 and 18. Molecular recognition between chiral hosts and... 

Some amide derivatives have been reported to form inclusion complex with a wide variety of organic compounds.9 Optically active amide derivatives are expected to include one enantiomer of a racemic guest selectively. According to this idea, some amide derivatives of tartaric acid (11-13) were designed as chiral hosts.10 As will be described in the following section, these amide hosts were found to be useful for resolution of binaphthol (BNO) (14) and related compounds (15,16). 

In the last two decades, chiral receptors containing amidic functions were designed almost exclusively for binding protected amino acids [49-57], oligopeptides [54,58], and lactic [59], tartaric [60,61] or camphoric acid derivatives [62]. Usually, chiral building blocks such as spirobifluorene [49, 60], binaphthalene [51,57],or amino acid chains containing macrocycles [52-56,58] were employed. An interesting receptor was synthesized via connection of the calix[4]arene moiety with an aza-crown derivative [61]. 

The mechanism of retention on chiral phases that is based on multiple hydrogen bonding formation involves the formation of base pairs and triple hydrogen bonds between the solutes and the chiral stationary phase 95 Fundamental work in this area has been done by Hara and Dobashi,96 97 using amino acid amide and tartaric acid amide phases. In addition, N,N -2,6-pyridinediyl bis(alkanamides) chemically bonded to silica gel have been described for the resolution of barbiturates 95... 

In Eq. (14), Yoda et al. [50] studied the preparation of optically active lactones, with three contiguous stereogenic centers, from imides with two stereogenic centers. The precursor chiral imide was easily prepared from tartaric acid. Silylation of the 2,3-diol and addition of lipophilic Grignard reagents to the imide gave the ( -hydroxy amide. The authors are investigating the stereochemical consequences of their work. 

Ketone syntheses. Reactivity discrimination between thiol esters and ordinary esters is the basis of an approach to chiral yalkylated butyrolactones from tartaric acid. Morpholine amides are simple substrates for Grignard reaction to provide ketones. ... 

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