Revised structure and synthesis of piperolein acids, guineensine and wisanine from Piper guineense
作者:S.K. Okwute、J.I. Okogun、D.A. Okorie
DOI:10.1016/s0040-4020(01)83507-9
日期:1984.1
The structures of piperolein acids guineensine and wisanine have been confirmed by synthesis, UV irradiation of trans piperolein B acid ester gave the cis-isomer reported in the literature as the trans-isomer. The trans-2, trans-4 ethylenic bonds in guineensine and wisanine were introduced by reacting piperolein B aldehyde and 2-methoxy piperonal with the appropriate Wittig or Reformatskyreagent.
Stereochemical control of the intramolecular Diels–Alder reaction by remote allylic substituents on the diene
作者:Michael J. Lilly、Michael S. Sherburn
DOI:10.1039/a701125c
日期:——
Intramolecular DielsâAlder reactions of substrates with
stereocontrolling elements attached to the diene terminus provide
exo-cycloadducts in good yields and high diastereofacial
selectivity.
The invention relates to compounds of the formula ##STR1## wherein R.sup.1 is hydrogen or lower alkyl; R.sup.2 is hydrogen or halogen; R.sup.3, R.sup.4 and R.sup.5 are hydrogen, acyl or lower alkyl; R.sup.6 and R.sup.7, independently, are hydrogen or lower alkyl; X is alkylene.sub.3-7 ; and n is an integer of zero to four; provided that only one of R.sup.3, R.sup.4 or R.sup.5 can be acyl; enantiomers thereof, and, when R.sup.7 is hydrogen, salts thereof with pharmaceutically acceptable bases. The compounds of formulas I and II are useful as agents for the treatment of allergic conditions.