Chiral pyrrolinones

In a study of the flash vacuum pyrolysis of chiral isopropylidene N-isopropyl-N-(a-methylbenzyl)aminomethylenemalonates, (/ )- and (S)-(1239), McNab and Monahan demonstrated the existence of another intermediate (1242) in the reaction pathway from the methyleneketene (1240) to the pyrrolinone (1243) [87CC138 88JCS(P 1)869]. Pyrolysis of the enantiomers (R) and (S) of compound 1239 resulted in the formation of an enantiomeric mixture of l-isopropyl-5-methyl-5-phenyl-2-pyrrolin-5-one (1243), where incomplete chirality loss was observed (see Scheme 50). 

Asymmetric synthesis of pyrrolidines and pyrrolinones. This chiral -hydroxy-amine (1) reacts with a y-keto acid in refluxing toluene to form a chiral bicyclic lactam 2 in 75-98% yield. Treatment of 2 with excess alane, generated from AlCly and LiAlH4,... 

Glycine anion equivalent. After a Lewis acid-catalyzed condensation with an aldehyde at C-5 and functional group protection, the degradation of the pyrrolinone ring unveils a )3-hydroxy-a-amino acid chain. More elaborate systems can be obtained from chiral aldehydes such as glyceraldehyde acetonide. 

Fluorescamine reacts efficiently with less common chiral a-amino adds to form pyrrolinone-type chromophores. The characteristic Cotton effects at 324-300 and 290-263 nm can be related to the absolute configuration of the parent a-amino acid without isolation of the products (Fig. 13). These... 

Figure 14. Negative or positive chirality arising from the interaction of the pyrrolinone-type chromophore with the carboxyl moiety of L-a-amino acid (or ester) or D-a-amino acid (or ester) (51 or 52, respectively). (From Toome and Wegrzynski, 1978. Reproduced with permission of Academic Press, Inc.)...

The elimination-addition of AB shown in Figure 5.2c is not limited to intermolec-ular reactions. DKR of racemic 5-hydroxy-2(5H)-furanones and N-acyl-5-hydroxy-2-(5H)-pyrrolinones can be performed by lipase-catalysed enantioselective acylation of the hydroxy groups using vinyl acetate (Scheme 5.36) [109]. This approach has also been extended for the DKR of hemiaminals as shown in Scheme 5.37 [110]. DMAP-based chiral catalyst containing 4-tert-butyl-l,3-thiazoline-2-thione moiety, which was reported as chiral auxiliary of acylation reagent, promotes efficient DKR by asymmetric acylation (Scheme 5.37) [110b]. 

Hydroxy-2(5H)-furanones were successfully involved in DKRs using lipase PS, offering an attractive route to the enantioselective synthesis of a series of 5-acyloxy-2(5H)-furanones with optimal chiral economy. In the same way, the corresponding 5-(acyloxy)pyrrolinones were submitted to esterification using Candida antarctica lipase B via DKR (Scheme 3.18). ... 

Use of the retro-Diels—Alder reaction in the synthesis of chiral pyrrolidine and pyrrolinone products has been described by several groups. The... 

More recently the a-methoxyethylanthracene system has been used to prepare chiral pyrrofidinone esters 54 (2010TA2719) and pyrrolinones 55 (2011OBC4353 Scheme 13). 

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