Total Synthesis of Peribysin E Necessitates Revision of the Assignment of its Absolute Configuration

Abstract

The right way round: Peribysin E, a naturally occurring adhesion inhibitor, has been synthesized and, as a result, its absolute configuration reassigned. The natural and nonnatural enantiomers can be reached starting from (R)‐ or (S)‐carvone, respectively. A key step is the ring contraction of 1 to 2 (see scheme, TBS=tert‐butyldimethylsilyl, TES=triethylsilyl).

Synthesis of the tetracyclic core of Illicium sesquiterpenes using an organocatalyzed asymmetric Robinson annulation

“…Deoxygenation of the C-15 primary alcohol was performed by: (a) mesylation of the alcohol with MsCl; and (b) reductive deoxygenation with LiEt 3 BH (super hydride). The thioketal protecting group was then removed under oxidative conditions with [bis(trifluoroacetoxy)iodo]benzene (PIFA) to yield ketone 10 in good yield (66% over three steps, Scheme 2) [78]. This approach allowed us to produce a sufficient amount of enone 10 (>10 grams) for further functionalization.…”

3.16 The Semipinacol Rearrangements

“…Only a few examples involve the participation of the hydroxyl group (related moiety), for instance, the key step of Danishefsky's total synthesis of peribysin E (Scheme 91). 109 In sharp contrast, ring expansion has much better applicability. Usually, thermally favorable expansions from three-to fourmembered ring or from four-to five-membered are well studied.…”

A practical deca-gram scale ring expansion of (R)-(−)-carvone to (R)-(+)-3-methyl-6-isopropenyl-cyclohept-3-enone-1

“…Synthetic approaches to the perhydroazulene structures from para-menthanes have involved the contraction of the sixmembered ring to cyclopentanoids followed by heptanyl-annulation, 30,31 or much less frequently expansion to cycloheptanoids and pentanyl-annulation. 32 This last strategy has been studied in our laboratory for the synthesis of cycloheptanoids, 33 and thus access to perhydroazulene terpenoids and alkaloids.…”