Hydroformylation Prelog-Djerassi lactone

Acetalization of oxo aldehydes is used to protect sensitive aldehyde products, especially in asymmetric hydroformylation preventing racemization of an a-chiral aldehyde product [18-22,27]. Acetal formation can also be applied to the synthesis of monocyclic or spirocyclic pyranes as potential precursors and building blocks for natural products such as pheromones or antibiotics. A representative example is the synthesis of the pyranone subunit of the Prelog-Djerassi lactone. For this purpose, various 1,2-disubstituted homoal-lylic alcohols were used (Scheme 3) [32],... 

Common substructural motifs in polyketide natural products are six-membered ring lactones, lactols, and tetrahydropyrans. It was recognized by Wuts and co-workers that hydroformylation of readily available homoaUyhc alcohols would provide a direct and efficient entry into these ring systems. Such an approach was employed in a synthesis of Prelog-Djerassi lactone (Scheme 5.11) [13]. 

Hydroformylation of 2,6-dimethyl-6-hepten-2-ol produces hydroxycitronellal (equation 12).22 Subjecting allyl alcohol to hydroformylation reaction conditions with HCo(CO>4 yields only propanal, isomerization taking place more rapidly than hydroformylation.2 Phosphine-modified rhodium catalysts will convert allyl alcohol to butane-1,4-diol under mild conditions in the presence of excess phosphine, however (equation 13).5 30 31 When isomerization is blocked, hydroformylation proceeds normally (equation 14). An elegant synthesis of the Prelog-Djerassi lactone has been accomplished starting with the hydroformylation of an allylic alcohol (equation IS).32... 

Hydroformylation of a secondary homoallylic alcohol such as 1 followed by PCC oxidation provides a useful route to the 8-lactone 2. The product was converted by known reactions into the Prelog-Djerassi lactone (3). ... 

The same authors reported about a short synthesis of the (+)-Prelog-Djerassi lactone benefiting from an asymmetric hydroformylation-crotylation one-pot reaction (Scheme 5.141) [30, 31]. The hydroformylation of vinyl 2,6,7-trioxabicyclo[2.2.2]octane was carried out with a (S,S,S)-BDP-based rhodium... 

Scheme 5.141 Synthesis of the (+)-Prelog-Djerassi lactone via an asymmetric hydroformylation-crotylation one pot reaction.

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See also in sourсe #XX -- [ ]

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