Asymmetric total synthesis of dendrobatid alkaloid 251F

The dendrobatid alkaloid (-)-251F was synthesized. The key steps of the synthesis were (1) an asymmetric Diels-Alder reaction to establish four of the necessary stereocenters in the target, (2) a ring-opening/ring-closing metathesis reaction to establish a key [3.3.0] bicyclic intermediate, and (3) an intramolecular Schmidt reaction.     

Synthesis of A-B-C-ring Tricyclic Core of iso-Merrilactone A

A desymmetrization approach for the synthesis of the A-B-C tricycle intermediate of iso-merrilactone A was described. The key steps of this synthesis to efficiently access the tetracyclic Illicium sesquiterpenes core included an intramolecular aldol cyclization and an oxidative lactonization reaction. A novel Au catalyzed hydrolytic cyclorearrangement cascade reaction was explored in the initial stage.     

Total synthesis of (+)-quassin

A total synthesis of (+)-quassin from naturally occurring (S)-(+)-carvone is described. The total number of steps was 28, and the overall yield was about 2.6%. The synthetic strategy for the construction of the tetracyclic carbon framework was based on a C-->ABC-->ABCD ring annulation sequence, involving an aldol reaction, an intramolecular Diels-Alder reaction, and an intramolecular acylation as the key steps. Subsequent functionalization of ring A and ring C then afforded the target (+)-quassin.     

Pseudo-domino palladium-catalyzed allylic alkylation/Mizoroki-Heck coupling reaction: a key sequence toward (±)-podophyllotoxin

A formal synthesis of podophyllotoxin was carried out in nine steps. The key pseudo-domino step was accomplished through the succession of an intermolecular palladium-catalyzed allylic alkylation and an intramolecular Mizoroki-Heck coupling reaction.     

An enantiodivergent formal synthesis of paecilomycine A

A concise, enantiodivergent formal synthesis of (+)-paecilomycine A and its antipode, involving a 1,4-chirality transfer protocol and an intramolecular Pauson–Khand reaction as the key steps is outlined.     

Total synthesis of (±) maoecrystal V

A concise first total synthesis of (±) maoecrystal V (1) is reported. The synthesis features a Wessely oxidative dearomatization of a phenol, an intramolecular Diels-Alder reaction, and a Rh-catalyzed O-H bond insertion as key steps.     

Stereoselective total synthesis of (+)-polyrhacitide A

A facile stereoselective total synthesis of secondary metabolite (+)-polyrhacitide A is described. Stereoselective aldol reaction, Horner-Wardsworth-Emmons reaction, Evans acetal intramolecular oxa-Michael reaction and diastereoselective syn reduction reaction are the key steps involved in the target synthesis.     

Convergent synthesis of panclicin-D via intramolecular SN2 displacement approach

A convergent enantioselective synthesis of panclicin-D has been reported from simple octanal using syn aldol reaction via intramolecular S_N2 displacement reaction for the first time towards the construction of anti-β-lactones in panclicin-D. The key steps involved are C-allylation, asymmetric aldolization under Crimmins condition, intramolecular S_N2 displacement, and Mitsunobu esterification reaction.     

First asymmetric total synthesis of (+)-sparteine

[reaction: see text] The total synthesis of (+)-sparteine was accomplished from 2,5-norbornadione in 15 steps and 15.7% overall yield. The key steps were two ring-expansion reactions, one involving an intramolecular Schmidt reaction and one using a novel variant of the photo-Beckmann rearrangement.     

Concise total synthesis of antiarrhythmic drug dronedarone via a conjugate addition followed intramolecular heck cyclization

A concise, scalable, and an efficient total synthesis for dronedarone ( 2 ) was described using conjugate addition followed by intramolecular Heck cyclization. The other key reaction includes selective reduction of nitro functionality and addition of lithiated terminal alkyne to the aldehyde. The overall yield of this approach is 44% in six steps.     

Total synthesis of (-)-Przewalskin B

The first total synthesis of (-)-Przewalskin B has been accomplished with an intramolecular nucleophilic acyl substitution (INAS) reaction and an intramolecular aldol condensation as key steps.     

Total synthesis of the marine alkaloid (-)-lepadin B

An enantioselective total synthesis of (-)-lepadin B has been developed starting from (2S,4S)-2,4-O-benzylidene-2, 4-dihydroxybutanal. The key steps in the synthesis include the use of an aqueous intramolecular acylnitroso Diels-Alder reaction to afford the trans-1,2-oxazinolactam and Suzuki cross-coupling reaction to elaborate the (E,E)-octadienyl unit.     

Synthetic studies on the DEF-rings of FR182877 and hexacyclinic acid

A synthesis of model DEF-rings of the polyketide anti tumor natural products FR182877 and hexacyclinic acid has been achieved. The key steps in the synthesis are an intramolecular Pd(0) catalyzed allylic substitution reaction, which was used to generate a 9-membered carbocycle, and a novel transannular iodocyclization reaction which furnished the DF-rings of both natural products.     

Total synthesis of jimenezin via an intramolecular allylboration

[structure: see text] An efficient total synthesis of the annonaceous acetogenin jimenezin was achieved. The key steps used were a highly stereoselective intramolecular allylboration to establish the tetrahydropyran ring and an intramolecular Williamson reaction to close the tetrahydrofuran ring.     

A new beta-carbolinone synthesis using a Rh(II)-promoted [3 + 2]-cycloaddition and Pd(0) cross-coupling/Heck cyclization chemistry

[reaction: see text]. A short and efficient synthesis of the beta-carbolinone ring system was achieved using a rhodium(II)-catalyzed [3 + 2]-cycloaddition, a Pd(0)-catalyzed C-N amination reaction, and a subsequent intramolecular Heck reaction as the key synthetic steps.     

Application of oxetane ring opening toward stereoselective synthesis of zincophorin fragment

A stereoselective synthesis of the C1–C11 fragment of zincophorin was achieved by using an intramolecular oxetane ring opening reaction as the key step. The oxetane moiety was synthesized by employing a desymmetrization protocol developed at our group and a non-Evans syn aldol as the key steps toward the synthesis.     

Solid-phase total synthesis of the pentacyclic system lamellarins U and L

[reaction: see text] A total solid-phase synthesis of lamellarins U and L has been achieved. The conversion of an aldehyde group into a formate by a Baeyer-Villiger reaction and a intramolecular [3 + 2] cycloaddition of a 3,4-dihydroisoquinolinium salt over a triple bond comprise the key steps of the process. Each transformation has been controlled with the proper spectroscopic and analytical methods.     

A formal total synthesis of Lycopodium alkaloid, (±)-magellanine, by using the intramolecular Pauson Khand reaction

A formal total synthesis of magellanine was accomplished by using the stereoselective Ireland-Claisen rearrangement and the intramolecular Pauson-Khand reaction of exocyclic enynes as key steps.     

Total synthesis of (+)-yohimbine via an enantioselective organocatalytic Pictet-Spengler reaction

The binolphosphoric acid-catalyzed Pictet-Spengler reaction of an N-(5-oxy-2,4-pentadienyl)tryptamine derivative with methyl 5-oxo-2-(phenylseleno)pentanoate leads to the tetrahydro-β-carboline in a 92:8 enantiomeric ratio. This product is easily converted into the substrate for a stereoselective intramolecular Diels-Alder reaction of the type earlier reported by Jacobsen. These two key steps constitute the basis for a nine-step total synthesis of (+)-yohimbine from tryptamine. A similar asymmetric Pictet-Spengler reaction was applied to the synthesis of an intermediate in the recent total synthesis of corynantheidine by Sato.     

Enantioselective Total Synthesis of (+)‐Steenkrotin A and Determination of Its Absolute Configuration

The first enantioselective total synthesis of (+)‐steenkrotin A has been achieved in 18 steps and 4.2 % overall yield. The key features of the strategy entail a Rh‐catalyzed O?H bond insertion followed by an intramolecular carbonyl‐ene reaction, two sequential SmI₂‐mediated Ueno–Stork and ketyl–olefin cyclizations, and a cascade intramolecular aldol condensation/vinylogous retro‐aldol/aldol process with inversion of the relative configuration at the C7 position. The absolute configuration of (+)‐steenkrotin A was determined based on the stepwise construction of the stereocenters during the total synthesis.