Tartrate-derived diammonium salt

A more general and highly diastereoselective Mannich-type reaction was developed by Ohshima and Shibasaki. The tartrate-derived diammonium salt 43c possessing 4-fluorophenyl substituents was identified as an optimal catalyst for the reaction of 28 with various N-Boc imines under solid (Cs2CC>3)-liquid (fluoroben-zene) phase-transfer conditions, as exemplified in Scheme 4.24 [64]. The usefulness of the Mannich adduct 67b was further demonstrated by the straightforward synthesis of the optically pure tripeptide 68. 

In the past decade, several other structural motifs were used for the development of effective chiral PTC. In 2002, Shibasaki and co-workers [61] demonstrated the high potential of tartaric acid-derived bidentate PTC. They reported the preparation and evaluation of tartrate-derived diammonium PTCs of type XXXV for alkylation of 1 with activated alkyl halides (Scheme 8.6), and the salt XXXVa was foimd to be optimal PTC for asymmetric alkylation reactions from more that 70 constructed tartrate-based ammonium salts [62]. 

MacFarland and co-workers [63] reported the preparation of more sterically demanding tartrate-derived diammonium salts XXXVI but they showed only limited... 

Shibuguchi T, Mihara H, Kuramochi A, Ohshima T, Shibasaki M (2007) Catalytic Asymmetric Phase-Transfer Michael Reaction and Mannich-Type Reaction of Glycine SchiffBases with Tartrate-Derived Diammonium Salts. Chem Asian J 2 794... 

Shibuguchi T, Mihara H, Kuromachi A, Ohshima T, Shibasaki M. Catalytic asymmetric phase-transfer Michael reaction and Mannich-type reaction of glycine Schiff gases with tartrate-derived diammonium Salts. Chem. Asian J. 2007 2(6) 794-801. 

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