Direct addition of a chiral N-azidoacetyl thiazolidinethione to a variety of dialkyl acetals catalyzed by a commercially available and structurally simple nickel(II) complex gives access in good yields and a highly stereocontrolled manner to anti-β-alkoxy-α-azido carboxylic derivatives which, in turn, can be easily converted into a wide array of enantiomerically pure compounds.

The structurally simple (Me3P)2NiCl2 complex catalyzes SN1-type alkylations of chiral N-acyl thiazolidinethiones with diarylmethyl methyl ethers and other stable carbenium cations. The former can contain a variety of functional groups and heteroatoms at the α-position. The resultant adducts are isolated as single diastereomers in high yields and can be converted into enantiomerically pure derivatives in a straightforward manner.

Protected peptides containing an anti β‐hydroxy tyrosine are synthesized in a straightforward and highly efficient manner through the direct and stereoselective addition of N‐azidoacetyl‐4‐isopropyl‐1,3‐thiazolidine‐2‐thione to dialkyl acetals catalyzed by a nickel(II) complex, the forging of an amide bond by removal of the chiral auxiliary with an amino ester, and final coupling with a third amino acid.

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Stereoselective Alkylation of (S)-N-Acyl-4-isopropyl-1,3-thiazolidine-2-thiones Catalyzed by (Me 3P)2NiCl2. -All alkylation products are isolated as single diastereoisomers which can be converted into enantiomerically pure derivatives after simple removal of the chiral auxiliary (not shown). -(FERNANDEZ-VALPARIS, J.; ROMO, J. M.; ROMEA*, P.; URPI, F.; KOWALSKI, H.; FONT-BARDIA, M.; Org. Lett. 17 (2015) 14, 3540-3543, http://dx.