Formal synthesis lepadiformine

Short Syntheses of (+)-Cylindricine and Formal Synthesis of (-)-Lepadiformine... 

In 2006, Shibasaki and co-workers [91] developed phase-transfer-catalyzed asymmetric Michael addition of glycine Schiff base 237 and dienone 238 to afford dienone 240 in 84% isolated yield and 82% ee for the total synthesis of (+)-cylin-dricine C (242) and a formal synthesis of (—)-lepadiformine (244), using a chiral two center organocatalyst 239 (TaDiAS Tartrate-derived Di-Ammonium Salt) (Scheme 17.41). (+)-cylindricine C (242) was achieved three steps from 240 using... 

Mihara H, Shibuguchi T, Kuramochi A, Ohshima T, Shibasaki M (2007) Short Synthesis of (-t)-Cylindricine C and Formal Total Synthesis of (-)-Lepadiformine. Heterocycles 72 421... 

The Shibasaki group also demonstrated the potential of their Ca-symmetric diammonium salt catalyst 135 for the syntheses of the alkaloids (+)-cylindricine C (138) and (—)-lepadiformine (139) [22c,68,69], By applying a PT-catalyzed addition of Schiff base 140 to Michael acceptor 141, the key intermediate 142 was obtained in good yield and with good enantiomeric excess. Compound 142 could then be used to obtain selectively either the cylindricine C precursor 143 or the lepadiformine synthon 144 in a very efficient tandem cyclization reaction by choosing the optimum reagents. The impressively short total synthesis of (+)-cylindricine C (138) could be achieved in only two additional steps, whereas the synthesis of the tricyclic intermediate 144 represents a formal total synthesis of (—)-lepadiformine (139) (Scheme 28). 

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