Enantioselective Synthesis of L- and D-Carboranylalanine.
The enantioselective synthesis of L- and D-carboranylalanine is reported. Imides 13 and 14 are treated with titanium tetrachloride, DIEA, and NBS to introduce a bromo functionality in 98:2 ratio at the alpha-center. Azide displacement with TMGA, displacement of the oxazolidinone template with titanium tetrabenzyloxide, and subsequent hydrogenolysis permits L- or D-carboranylalanine to be isolated in high stereoselectivity and 35-40% yields overall.
Radel
Peggy A.
PA
Department of Pharmaceutical Chemistry, University of California, San Francisco, California 94143-0446.
Kahl
Stephen B.
SB