Total synthesis of (±)-dihydroactinidiolide using selenium-stabilized carbenium ion

A new, short total synthesis of dihydroactinidiolide 1 is described using selenium carbenium ion-promoted carbon–carbon bond formation as the key step. Our synthetic strategy starts with a lactonization reaction between 1,3,3-trimethylcyclohexene 13 and α-chloro-α-phenylseleno ethyl acetate 14, affording the key intermediate, α-phenylseleno-γ-butyro lactone 15, which reacted via a selenoxide elimination to the target compound 1.     

Total synthesis of (±)-marmin and related coumarin monoterpenes

(±)-Marmin (1a) and its cis isomer (1b) have been synthesized from 7-neranyloxycoumarin (10a) and 7-neryloxycoumarin (10b), respectively, by way of the corresponding terminal epoxides 2a and 2a. The geometrically and positionally specific route confirms the structure and, in particular, the irons double bond geometry of natural (+)-marmin and epoxide (+)-2a. The latter, upon reaction with stannic chloride in benzene gives rise to the naturally occurring cyclic monoterpene coumarin types 3 and 6 as well as the previously unknown double-bond isomer 13.     

Total Synthesis of (±)-Iridolactone

A total synthesis of (±)-iridolactone ( 1 ) from bicyclo[2.2.1]ketone 6 is described. Trisubstituted cyclopentenoid aldehyde 7 is a key intermediate.     

Total Synthesis of (±)-Barbatusol

The naturally occurring hypotensive agent barbatusol (1a) has been synthesized in racemic form from 3-isopropylveratrole and 4,4-dimethyl-2-cyclohexene-1-one. An improved procedure for deprotection of barbatusol dimethyl ether (1b) is described.     

Total Synthesis of (±)-Gelsemine

A complex molecular reorganization ( 1 → 2 ), a sequential anionic aza-Cope rearrangement and Mannich cyclization, and an unprecedented intramolecular Heck reaction of the tetrasubstituted double bond of a vinylogous carbamate are key steps in a new total synthesis of (±)-gelsemine ( 3 ). MOM=methoxymethyl, DBU=1,8-diazabicyclo[5.4.0]undec-7-ene.     

Total Synthesis of (±)-Patriscabrol and (±)-Boschnialactone

A total synthesis of (±)-patriscabrol (1) and (±)-boschnialactone (2) is described. The cyclopentapyranone skeleton is assembled by means of Baeyer-Villiger oxidation of ketol 5.     

Total Synthesis of (±)-2-Pupukeanone

(±)-2-Pupukenone ( 4 ) has been synthesized, the key step being the intramolcular Diels-Alder reaction of the intermediate 13 to 14 (42%) and 15 (14%). The bromodiene 12 has been obtained from the reaction of α-isopropylidene-γ-lactone (Scheme 2) 12 with sodium phenylselenide and subsequent esterification to 9 , oxidation and thermal elimination of which furnished 10 . Reduction of 10 with diisobutylaluminimum hydride and treatment of the resulting alcohol 11 with PBr₃ led to the required bromodiene 12 . Finally, hydrogenation of the 14 on Pt(C) in CH₃OH gave a 4:1 mixture of 2-pupukeanone ( 4 ) and epi-2-pupukeanone 16 .     

The Total Synthesis of (±)-Camphor and (±)-Epicamphorenone from Methylcyclopentadiene

The total synthesis of (±)-carnphor and (±)-epicamphorenone from methylcyclopentadiene are described.     

The total synthesis of (±)-coriolin

The first total synthesis of (±)-coriolin from the tricyclo 6-4-5-fused ring photo-adduct through the key tricyclo 5-5-5-fused ring intermediate, 7,8,11 - trihydroxy - 1,4,4 - trimethyltricyclo[6.3.0.0^2,6]undecan - 3 - one, is described.     

A stereospecific synthesis of (±)-ferruginol

A stereospecific synthesis of (±)-ferruginol following the Robinson “ring extension” method has been described. The infra-red spectra of the benzoates of the synthetic and natural ferruginol are found to be identical.     

First total synthesis of (±)-oxerine

Total synthesis of (±)-oxerine (1), a monoterpene alkaloid, starting from 3-bromopyridine (7) is described. The key reaction in this sequence is the samarium iodide (SmI₂)-mediated intramolecular cyclization of γ-ethynyl bromide (4).     

First Total Synthesis of (±)-13-Hydroxyneocembrene

First total synthesis of (±)-13-hydroxyneocembrene ( 1 ), starting from 6-methyl-5-hepten-2-one ( 6 ) and geraniol ( 7 ), is described. The key steps are (i) the addition of sulfur-stabilized carbanion 12 to aldehyde 9 , (ii) the synthesis of 18 by using phase-transfer catalyzed coupling reaction, and (iii) low-valent titanium-induced intramolecular coupling of oxo aldehyde 3 to afford the target molecule after the final deprotection.     

A stereocontrolled total synthesis of (±)-norzizanone

A stereocontrolled total synthesis of (±)-norzizanone 1 has been efficiently accomplished involving base-induced rearrangement of the mesylate 17 as the key step. Aryl participated intramolecular cyclisation of the bromophenol 11 provided the tricyclic dienone 12, which was stereoselectively converted into the mesylate 17.     

A Stereoselective Total Synthesis of (±)-Maritimol, (±)-2-Deoxystemodinone, (±)-Stemodinone,and (±)-Stemodin

A simple and stereoselective total synthesis of (±)-maritimol ( 2d ) and its conversion into the other title compounds (±)-( 2a ), ((±)- 2b ), and ((±)- 2c ) is described. The unique bicyclo[3.2.1]octane moiety, constituting their C/D-ring system, is stereospecifically obtained by solvolytic rearrangement of the methanesulfonate 23 .