4-Butanolides, chiral

Chiral furanones (butanolides) such as 191 have been used as dipolarophUes in various 1,3-dipolar cycloadditions. The chiral 4-substituted butanolide 190 was prepared from 191 and the chiral auxiliary menthol (Scheme 12.55) (310,311). The single diastereomer 191 is obtained by crystallization and epimerization of the other diastereomer, as the amount of 191 in solution decreases. 1,3-Dipolar... 

Chiral -substituted 4-butanolides. (S)-( + )-2-(p-Tolylsulfinyl)-2-buten-4-olide (2), which can be prepared in several steps from propargyl alcohol (equation 1), is an effective Michael acceptor for stereocontrol led conjugate addition of Grignard reagents. 

The ee values in the enantioselective deprotonation are independent of the size of the attached alkyl residue. The method tolerates several substituents, e.g. 2- or 3-dibenzylamino, 3- or 4-(A(A-dialkylcarbamoyloxy), or 4-TBDMSO. Essentially enantiopure 2-hydroxy acids, 3-amino alkanols, 7-amino alkanols, cyclopropyl carbamates, and 2-hydroxy-4-butanolides " were obtained. Extraordinary high (>70) kinetic H/D isotope effects were observed in the deprotonation of chiral 1-deuteroalkyl carbamates. Kinetic resolution of racemic alkyl carbamates was achieved. ... 

Butanolides are ubiquitous subunits of a large number of bioactive com-poimds. Epoxy triflate sugars 1 and 2 open an easy access to selected polysubstituted chiral butanolides [36,37], by a two-step sequence. The first step is displacement of the triflyl group of 1 and 2 under extremely controlled conditions with a very reactive enolate of ferf-butyl acetoacetate followed by cycHzation under acid catalysis, which furnished 45 and 46 [36] (Scheme 9). 

Shimoda K, Kubota N, Hirata T, Kondo Y, Hamada H. Stereoselective reduction of 2-butenolides to chiral butanolides by reductases from cultured cells of Glycine max. Tetrahedron Lett. 2007 48 1345-1347. 

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