HCl; AcONa in ethanol; water dissoln. of PdCl2 in water cont. HCl, pH-adjustment to 5-6 (AcONa), addn. of 2 equiv. aldehyde (in EtOH), stirring for 20 min (pptn.); collection (filtration), washing (EtOH, ether), recrystn. (CHCl3);