219616-62-3Relevant academic research and scientific papers
Enzyme-catalyzed Reactions, Part 39. A Convenient Synthesis of Optically Active 5,5-Disubstituted 4-Amino- and 4-Hydroxy-2(5H)-furanones from (S)-Ketone Cyanohydrins
Buehler, Holger,Bayer, Andreas,Effenberger, Franz
, p. 2564 - 2571 (2007/10/03)
(S)-Ketone cyanohydrins (S)-2 are accessible by enantioselective HCN addition to ketones 1 by using hydroxynitrile lyase from Manihot esculenta ((S)-MeHNL) as a biocatalyst. Acylation of (S)-2 gave the corresponding (S)-acyloxynitriles (S)-3, which can be cyclized by LHMDS to give 5,5-disubstituted (S)-4-amino-2(5 H)-furanones (S)-4 and (S)-5. Different substituents (H, Me, OBn, OH) in the 3-position of the furanones were introduced by selecting the appropriate acylating agent, which in the case of benzyloxyacetyl chloride led to the novel structure type of 4-amino-3-hydroxyfuranones (S)-5. For the synthesis of 5,5-disubstituted (S)-tetronic acids (S)-8, ketone cyanohydrins (S)-2 were first transformed into the corresponding 2-hydroxy esters (S)-6. Acylation of (S)-6 gave 2-acyloxy esters (S)-7, which, by treatment with LHMDS or LDA, afforded tetronic acids (S)-8 in high yields and enantiomeric excesses. By debenzylation of benzyloxy acetoxy derivatives (S)-8 e,f, the new vitamin C analogues (S)-9a,b were generated. All the described tetronic acid and aminofuranone derivatives were obtained in good chemical yields and without racemization with respect to the starting cyanohydrins (S)-2. ln many cases the enantiomeric purity could be enriched by simple recrystallization (e.g. (S)-4a from 69% ee to >99% ee).
