Chemo-enzymatic synthesis of the azasugars 1,4-dideoxyallonojirimycin and 1,4-dideoxymannojirimycin

The enzymatic resolution of the N-phenylacetyl derivative of racemic homoserine lactone with penicillin G acylase immobilized on Eupergit C gave (R)-(+)-alpha-amino-gamma-butyrolactone and (S)-(-)-alpha-N-phenylacetamido-gamma-butyrolactone in high enantiomeric purity (ee >99%) and 46-47% yields for each enantiomer. The enantiomers were converted into azasugars 1,4-dideoxyallonojirimycin and 1,4-dideoxymannojirimycin using Wittig olefination, catalytic ring-closing metathesis (RCM), and stereoselective dihydroxylation with OsO4 in 29% overall yield over 11 high yielding steps. Enzyme inhibition studies showed that 1,4-dideoxyallonojirimycin is a better beta-glucosidase inhibitor (IC50 32.4 mu M toward beta-glucosidase from almonds) and a better beta-galactosidase inhibitor (IC50 5.9 mM for beta-galactosidase from Aspergillus oryzae) than 1,4-dideoxymannojirimycin (IC50 2.86 mM and 12.5 mM for beta-glucosidase and beta-galactosidase, respectively). (C) 2011 Elsevier Ltd. All rights reserved.