Spiro butyrolactone-pyrrolidine

Wang and co-workers further broadened the application of Cu(I)/TF-BiphamPhos catalyst system to the first catalytic asymmetric 1,3-dipolar cycloaddition of homoserine lactone-derived cychc aldimino esters with dimethyl maleate for the highly efficient synthesis of biologically active spiro-[butyrolactone-pyrrolidines] containing both a y-lactone and pyrrolidine moiety (Scheme 23) [43]. A key feature of this method is that the lactone ring in the generated spirocycles is provided by the dipole, rather than by the dipolarophile. 

Subsequently, Wang s group presented an unprecedented asymmetric exo-selec-tive 1,3-dipolar cycloaddition reaction of azomethine ylides with a-methylene-y-butyrolactone under the catalysis of a Cu(l)/DTBM-B1PHEP complex, providing an expedient and straightforward access to a series of enantiomerically enriched spiro-[butyrolactone-pyrrolidine] derivatives bearing one to two spiro quaternary stereogenic centers with excellent levels of stereocontrol (Scheme 24) [44]. 

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