1-C4)-alkyl or (C2-C4)-alkenyl)-Ar or Ar; wherein the stereochemistry at carbon position 1 is R or S; provided that when n=1 then B is not methyl, ethyl, propyl or butyl when D is butyl or methyl; and provided that when n=1 then D is a group other than phenyl and B is a group other than benzyl, and when n=2 then B is not methyl or t-butyl. 8.