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The treatment of the N-benzyloxycarbonyl α-methyl esters of L-glutamine or L-asparagine with tert-butyl nitrite in refluxing acetonitrile results in selective hydrolysis of the amide group, giving optically pure Z-Glu-OMe (74%) or Z-Asp-OMe (88%); these are versatile chiral building blocks, and an efficient synthesis of cis-5-hydroxy-L-pipecolic acid from Z-Glu-OMe is described.

Very high asymmetric induction is observed in the aza-Diels–Alder reaction between dienes and the imine (R)-PhMeCH–NCHCO2PhMen*(where PhMen*= 8-phenylmenthyl), which bears matched auxiliaries on nitrogen and on the ester; reactions in trifluoroethanol, in the presence of trifluoroacetic acid (1 equiv.), give substituted pipecolic acid derivatives in ca 50% isolated yield, with only a single regio- and diastereo-isomer of the cycloadduct detectable in all cases (d.e.>95%).

A rapid entry into the C(9)–C(17) fragment of the avermectins is described which uses a [2,3] sigmatropic rearrangement of a functionalised allylic ether as the key step.