Aldehydes aldol type reactions reductive coupling

The synthesis pathway of quinolizidine alkaloids is based on lysine conversion by enzymatic activity to cadaverine in exactly the same way as in the case of piperidine alkaloids. Certainly, in the relatively rich literature which attempts to explain quinolizidine alkaloid synthesis °, there are different experimental variants of this conversion. According to new experimental data, the conversion is achieved by coenzyme PLP (pyridoxal phosphate) activity, when the lysine is CO2 reduced. From cadeverine, via the activity of the diamine oxidase, Schiff base formation and four minor reactions (Aldol-type reaction, hydrolysis of imine to aldehyde/amine, oxidative reaction and again Schiff base formation), the pathway is divided into two directions. The subway synthesizes (—)-lupinine by two reductive steps, and the main synthesis stream goes via the Schiff base formation and coupling to the compound substrate, from which again the synthetic pathway divides to form (+)-lupanine synthesis and (—)-sparteine synthesis. From (—)-sparteine, the route by conversion to (+)-cytisine synthesis is open (Figure 51). Cytisine is an alkaloid with the pyridone nucleus. 

As outlined in Scheme 28, the synthesis of the P-ketophosphonate 131 began with a one-pot anh -aldol/reduction step between ethyl ketone 101 and aldehyde 133, giving the 1,3-syn diol 134 (>30 ldr) [130, 132-136, 145, 146], The diol 134 was then converted into the carboxylic acid 135 in six steps. Completion of the subunit 131 required conversion into the acid chloride and reaction with the lithium anion of methyl-(di-l,l,l-trifluoroethyl)-phosphonate. The C9-C24 aldehyde 132 was prepared in two steps from 136, an intermediate from previous routes [55-58], The Still-Gennari-type coupling of 131 and 132 was readily achieved via treatment with... 

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