Amides cyclic, resolution

Following resolution with (—)-quinine, (+)-465 was transformed into the (-l->2-formamido derivative which was condensed with the acid chloride of (+)-465 to give the secondary amide 468. From this point, the cyclic imidate salt 469 was prepared, but cyclization to the dodecahedrane nucleus could not be realired With Thiele s add as starting material, several routes to triquinacene and 2,3-dihydrotriquinacen-2-one 462) have been developed Triquinacene reacts with Mo(CO)g to give tricarbonyl(triquinacene)molybdenum (470) and with (CHjCI -... 

The application of antibiotics as chiral selectors has resulted in the successful resolution of almost all types of neutral, acidic, and basic racemic molecule. These antibiotics have been used for the enantiomeric resolution of amino acids, their derivatives, peptides, alcohols, and other pharmaceuticals. The selectivities of the most commonly used antibiotic-based (vancomycin, teicoplanin, and ristocetin A) CSPs varied from one racemate to another and are given in Table 1. Vancomycin was used for the chiral resolution of amino acids, amines, amides, imides, cyclic amines, amino alcohols, hydantoins, barbiturates, oxazolidinones, acids, profens, and other pharmaceuticals. Teicoplanin was found to be excellent chiral selector for the enantiomeric resolution of amino acids, amino alcohols, imides, peptides, hydantoins, a-hydroxy and halo acids, and oxazolidinones, whereas ristocetin A is capable of chiral resolution of amino acids, imides, amino... 

This chapter covers the kinetic resolution of racemic alcohols by formation of esters and the kinetic resolution of racemic amines by formation of amides [1]. The desymmetrization of meso diols is discussed in Section 13.3. The acyl donors employed are usually either acid chlorides or acid anhydrides. In principle, acylation reactions of this type are equally suitable for resolving or desymmetrizing the acyl donor (e.g. a meso-anhydride or a prochiral ketene). Transformations of the latter type are discussed in Section 13.1, Desymmetrization and Kinetic Resolution of Cyclic Anhydrides, and Section 13.2, Additions to Prochiral Ketenes. 

The preferred formation of the kinetically favored (Z)-silylketene acetal with amide bases in THF can be rationalized by a cyclic transition state model (128) that enables a close interaction between Li cation, carbonyl oxygen and base (Scheme 23). The presence of additives such as HMPA or DMPU results in a greater degree of solvation of the lithium cation and a weakened Li -caibonyl oxygen interaction. Accordingly, the association between base and ester is diminished and the 1,3-diaxial strain in transition state (129) is reduced, whereas transition state (128) is still destabilized by A -strain." In the presence of a slight excess of ester in the enolization mixture, a kinetic resolution process accounts for an additional increase in the ratio of the ( )- vj. the (Z)-lithium enolate (Table 3). ° ... 

In this context, van Rantwijk and Sheldon reported in the last decade some remarkable examples of the potential of serine hydrolase for the enantioselective acylation of amines [183]. Here, more recent reactions will be discussed starting with KR of primary and secondary racemic amines and a few examples of the desymmetrization of diamines, a reaction that has scarcely been exploited. Acylation reactions are quite selective transformations for the formation of the desired final optically active amines and amides however, in some cases, a sister reaction such as the alkoxycarbonylation process using a carbonate instead of an ester will be mentioned in order to present some advantages, especially for the resolution of secondary cyclic amines. 

Based on the structural similarities of amino acid amides with ACL, we predicted that ACL racemase catalyzed the racemization of not only the cyclic amino lactam compounds but also amino acid amides. We soon discovered that ACL racemase from Achromobacter obae catalyzed the racemization of amino acid amides, such as 2-aminobutyramide and alanine amide [22], A previous study demonstrated that D-alanine was produced efficiently from L-alanine amide by a dynamic kinetic resolution reaction when the enzyme was used together with DAP from O. anthropi [23]. It had previously been unclear whether ACL racemase catalyzed the racemization of simple amino acid amides. 

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