A protecting-group-free synthesis of arbusculone, andirolactone, pinnatolide, ipomolactone, cyclocapitelline and isocyclocapitelline

Evolution of Strategies in Protecting‐Group‐Free Synthesis of Natural Products: A Recent Update

“…[ 30e ] Cyclocapitelline ( 58b ) and isocyclocapitelline ( 58a ) were isolated from rubiaceae family. [ 30f,30g ] Mohapatra and co‐workers [ 31a ] achieved a collective synthesis of all the above mentioned natural products from chiral pool material ( R )‐linalool ( 49 ) (Scheme 7A). Allylic oxidation of 49 with SeO 2 followed by NaBH 4 reduction afforded allylic alcohol, which on epoxidation with m ‐CPBA delivered the THF compounds 50a and 50b in 1:1 ratio.…”

“…However, the rearrangement of 51a to 52 and the oxidative degradation of 55a to 56 were quite unique in this collective synthesis. An early synthesis of (±)‐andirolactone by Quayle and Ward [ 31b ] (1994) was completed from 4‐methyl‐3‐cyclohexenone in 8 steps and 3 % overall yield. The racemic synthesis by Dethe and co‐workers [ 31c ] (2015) involved 4 steps from limonene and 47 % overall yield.…”

“…An early synthesis of (±)‐andirolactone by Quayle and Ward [ 31b ] (1994) was completed from 4‐methyl‐3‐cyclohexenone in 8 steps and 3 % overall yield. The racemic synthesis by Dethe and co‐workers [ 31c ] (2015) involved 4 steps from limonene and 47 % overall yield. (+)‐Pinnatolide synthesis by Tietze and co‐workers [ 31d ] required 9 steps and had an overall yield of 24 %.…”

“…The racemic synthesis by Dethe and co‐workers [ 31c ] (2015) involved 4 steps from limonene and 47 % overall yield. (+)‐Pinnatolide synthesis by Tietze and co‐workers [ 31d ] required 9 steps and had an overall yield of 24 %. However, it required improvement of diastereoselectivity by derivatization and recrystallization.…”

Asymmetric Organocatalytic [2,3]‐Wittig Rearrangement of Cyclohexanone Derivatives

“…The [2,3]-Wittig rearrangement has been widely exploited as a key reaction for the synthesis of different biologically active compounds. [3][4][5][6][7][8][9] Despite its widespread use, the number of asymmetric catalytic methods is still limited. [10] Our group previously reported an asymmetric [2,3]-Wittig rearrangement of oxindole, malonate and cyclopentanone derivatives, in addition to an example of a diastereoselective [2,3]-sigmatropic rearrangement of N-allyl ammonium ylides.…”