“…10 Over the past decade, a number of similar syn-aldol reactions have been realized in laboratory (though, with a somewhat lower stereoselectivity) in the presence of properly designed primary aminocatalysts. Among them, O-protected serine or threonine amino acids, [11][12][13][14][15][16] their amides, 17 valine, 18 leucine, 19 iso-leucine 20 or tert-leucine derivatives 21 and some primary-tertiary 1,2-diamine organocatalysts [22][23][24][25][26][27] exhibited promising catalytic performance. However, unlike enzymes, these valuable catalysts could be used just once and until recently no information on their recovery and reuse in the catalytic process has been available.…”