Indoloquinolizidine aldehydes

The second synthesis (398) is an extraordinarily simple and direct one, in which the protected tetracyclic indoloquinolizidine aldehyde 741, obtained as two C-14 epimers and prepared as shown in Scheme 113, was subjected to cleavage of the 3,A b-bond by reaction with benzyl chloroform-ate in aqueous tetrahydrofuran. The resulting C-3 alcohol was converted into the corresponding nitrile 742, which was again obtained as a mixture of C-14 epimers, regardless of whether the starting material 741 was either... 

A recent formal synthesis of the alkaloid (—)-mitralactonine relied on a reaction that allowed the simultaneous creation of three new bonds, two of them a and one ft with respect to the quinolizine nitrogen. As shown in Scheme 112, treatment of triptamine with chiral aldehyde 480 in the presence of acid directly gave a mixture of diastereo-meric indoloquinolizidines 481 and 482 through a mechanism involving a Pictet-Spengler cyclization and a N-alkylation reaction <2007SL79>. 

The group of Rueping has developed an enantioselective synthesis of chromenones through a Michael reaction and cychzation process between diketones and unsaturated aldehydes [136]. Furthermore, this reaction can be also followed with the addition of tryptamine to afford indoloquinolizidines [137]. An aza-MBH reaction was used in the enantioselective synthesis of isoindoHnes. In this... 

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