Stereodivergent amine synthesis

Figure 7.7 Stereodivergent amine synthesis reductant directed diastereomeric product formation with the (R) tert butylsulfinamide auxiliary.

Scheme 25. Stereodivergent synthesis of 1-dcoxy azasugars of the nojirimycin type by enzymatic aldolization followed by catalytic reductive amination. a) 1. Aldolase, DHAP 2. phosphatase 3. H2/Pd-C...

As shown in Scheme 14.9a,b, an efficient protocol for the stereoselective synthesis of 1,3-syn and -anti tetrahydropyrimidinones (syn- and anti- 2) could be developed [13]. The modular procedure is based on a stereodivergent cycliza-tion of readily available urea-type substrates 41 by intramolecular allylic substitution. The cychzation proceeds with excellent yield (up to 99%) and selectivity (up to dr > 20 1), purely based on substrate control. The product pyrimidines 42 can be readily transformed into the corresponding free syn- and anti-amines 43. Furthermore, also a novel domino sequence for the rapid assembly of 1,3-syn-substituted oxazines 46 could be realized [14]. Mechanistically, the one-pot procedure is based on a three-step sequential process involving a hemi-aminalization... 

Back TG, Wulff JE. A stereodivergent synthesis of virantmycin by an enzyme-mediated diester desymmetrization and a highly hindered aryl amination. Angew. Chem. Int. Ed. 2004 43(47) 6493-6496. 

Figure 21 Stereodivergent synthesis of 1-deoxy aza sugars of the nojirimycin type by two-step enzymatic aldolization/catalytic reductive amination [92,119-124],...

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