This article presents comprehensive studies on the application of primary, secondary, and tertiary amines as efficient organocatalysts for the de novo synthesis of ketoses and deoxyketoses. Mimicking the actions of aldolase enzymes, the synthesis of selected carbohydrates was accomplished in aqueous media by using proline- and serine-based organocatalysts. The presented methodology also provides direct access to unnatural L-carbohydrates from the (S)-glyceraldehyde precursor. Determination of the absolute configuration of all obtained sugars was feasible using a methodology consisting of concerted ECD and VCD spectroscopy.

An improved and convenient preparation of protected (S)‐isoserinal on a large scale is reported. This key intermediate was reacted through organocatalyzed aldol reaction or Wittig based chain extension and functionalization to give enantiopure 1,5,6‐trideoxy‐1,5‐imino‐hexitols such as 10a (L‐manno) and 10b (D‐gluco). These two compounds are of interest as glycosidase inhibitors. The elaborated organocatalytic process includes diastereoselective syn aldol reaction of (S)‐isoserinal hydrate and hydroxyacetone or 1‐hydroxy‐2‐octanone and is promoted by various amino acid‐based catalysts. Diastereoselectivities of up to 8:1 were achieved, thus establishing a new, efficient synthetic route to these important carbohydrate mimics.

Herein we report a short and efficient protocol for the synthesis of naturally occurring higher‐carbon sugars—sedoheptulose (d‐altro‐hept‐2‐ulose) and d‐glycero‐l‐galacto‐oct‐2‐ulose—from readily available sugar aldehydes and dihydroxyacetone (DHA). The key step includes a diastereoselective organocatalytic syn‐selective aldol reaction of DHA with d‐erythrose and d‐xylose, respectively. The methodology presented can be expanded to the synthesis of various higher sugars by means of syn‐selective carbon–carbon‐bond‐forming aldol reactions promoted by primary‐based organocatalysts. For example, this methodology provided useful access to d‐glycero‐d‐galacto‐oct‐2‐ulose and 1‐deoxy‐d‐glycero‐d‐galacto‐oct‐2‐ulose from d‐arabinose in high yield (85 and 74 %, respectively) and high stereoselectivity (99:1).

The direct asymmetric aldol reaction of α-ketoesters catalyzed by chiral tertiary amines is reported. The described methodology is characterized by mild reaction conditions and distinct product selectivity determined by the starting materials. In the developed transformation pyruvates undergo highly selective self-condensation reaction, whereas cross-aldol reaction take place predominantly for their carbon chain homologues in presence of aldehyde acceptors. Notably, addition of bulky phenol moiety into pyruvate inhibit the spontaneous lactonization of products and enhance the enantioselectivity.

A short synthesis of iminosugars and pipecolic acid derivatives has been realized through aldol addition of a pyruvate, a range of ketones and (S)-isoserinal, followed by catalytic reductive intramolecular amination. The stereoselective aldol reaction was achieved successfully by using tertiary amines or di-zinc aldol catalysts, thus constituting two parallel routes to optically pure products with good yields and high diastereoselectivities. These carbohydrate analogues may be the inhibitors of potent glycosidases and glycosyltransferases.