Asymmetric synthesis of pipecolic acid

A reaction related to alkene-aldehyde coupling is the alkene-imine coupling. A one-pot cyclization involving such a reaction (Eq. 3.27) proceeds smoothly in a mixture of water-THF. The reaction has been used in the asymmetric synthesis of pipecolic acid derivatives.114... 

From the many examples of reactions with imines activated in various ways, we select the asymmetric synthesis of pipecolic acids by double diastereomeric induction using an activated imine 87 with two chiral auxiliaries - a-methylbenzylamine on the nitrogen atom and 8-phenylmenthol as esterifying group. Both these auxiliaries were discussed in earlier chapters (22 and 27). Acid-catalysed cycloaddition with normal dienes gives excellent asymmetric induction and reasonable yield. We show the matched case - the mismatched case is obviously worse.13... 

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