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Towards a Total Synthesis of Phenalinolactone Core Diterpenoid 6: Synthesis of a Racemic Decahydrobenzocyclobutaisobenzofuran with a trans‐anti‐cis Junction of the Isocyclic Rings
Author(s) -
Hampel Thomas,
Brückner Reinhard
Publication year - 2017
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/ejoc.201700198
Subject(s) - chemistry , annulation , intramolecular force , ring (chemistry) , stereochemistry , cyclohexanone , cyclohexene , cyclohexane , total synthesis , epoxide , catalysis , organic chemistry
Synthetic efforts towards the “phenalinolactone core diterpenoid 6” ( 5 ) are described. It contains a cyclohexyl alcohol (A ring), a cyclohexane (B ring), and a cyclohexene (C ring), which are angularly annulated trans and cis , respectively. What makes them unique is the trans ‐ (or “ anti ”‐) relationship between the A and the C ring. The trans ‐configured A/B ring junction was established in a novel cyclohexanone annulation. Anti ‐selective cis ‐annulations of the C ring failed when attempted with intramolecular Diels–Alder reactions with dienes of varied electron demand ( 21 , 31 ). In contrast, an anti ‐selective cis ‐annulation of a C ring precursor based on an intramolecular [2+2]‐photocycloaddition succeeded. It provided the tetracycle 38 in 70 % yield. It contains a densely functionalized four‐membered ring. It should lend itself to ring‐opening(s) and/or rearrangement(s). Accordingly, compound 38 should be adoptable to proceeding to the target structure 5 in future work.