Hydroxy aldehydes butyric aldehyde

P-hydroxy butyr-aldehyde Solvent Perfume, dyes, sedative (drugs) Skin irritant in concentrated form... 

Aldol CHs—CH(OH)—CH2—CHO. jS-Hydroxy Butyric Aldehyde This compound is an important and interesting member of the group. It is made by the condensation of two molecules of acet-alde-hyde (p. 116). The reaction is, therefore, known as the aldol condensation and-in its general form is characteristic of aldehydes taking place also with the hydroxy aldehydes, e.g., with glycolic aldehyde,... 

Aldol is oxidizable to hydroxy butyric acid and, being a heta-hydroxy compound, loses water yielding an unsaturated aldehyde, crotonic aldehyde (p. 169), as in the second part of the reaction. 

With benzaldehyde 144 or halogenated derivatives (Cl, F) as acceptors the yeast-PDC-catalyzed addition proceeds with almost complete stereoselectivity to furnish the corresponding (R)-configurated 1-hydroxy-1-phenylpropanones 145 [447]. For practical reasons, whole yeast cells are most often used as the catalyst, with only small loss of enantioselectivity [423,424]. The conversion of benzaldehyde in particular has gained industrial importance because the acyloin is an important precursor for the synthesis of L-(-)-ephedrine [448]. Otherwise, the substrate tolerance is remarkably broad for aromatic aldehydes on the laboratory scale, however, yields of acyloins are usually low because of the prior or consequent reductive metabolism of aldehyde substrate and product, giving rise to considerable quantities of alcohol 146 and vicinol diols 147, respectively [423,424,449], The range of structural variability covers both higher a-oxo-acids (e.g. -butyrate, -valerate) as the donor component, as well as a,/J-un-saturated aldehydes (e.g. cinnamaldehyde 148) as the acceptor [450]. 

Amino-2-hydroxy[4- C]butyric acid (the corresponding aldehyde has been condensed with o-aminobenzaldehyde to give vasicine 4-hydroxy-[2- C]glutamic acid (found with vasicine in Linaria yw/garis ), N-methyl-anthranilic acid, and N-formylanthranilic acid have been tested as vasicine precursors in A. vasica, without success. 

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