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The total synthesis of the indole alkaloid (-)-andranginine has been achieved in 10 steps. Key reactions of the synthesis include a nucleophilic addition of acetylenyl anion to chiral

The skeleton of lucidumone was constructed through oxidative dearomatization/intramolecular Diels-Alder reaction, Cu-mediated remote C-H hydroxylation, allyl oxidation, acid-promoted dynamic kinetic resolution cyclization, and benzylic oxidation.

An efficient visible light photoredox catalyzed aerobic deprotection of 1,3-oxathiolanes using organic dye Eosin Y as a photocatalyst is disclosed. The deprotection procedure features the use of a metal-free catalyst, mild conditions, a broad range of substrate scope, and good functional group tolerance. 35 examples were tested under the standard conditions and most of them afforded the deprotected products in modest to high yields.

A double cyclization strategy was developed to construct the common tetracyclic core of calyciphylline B-type alkaloids. Key features of the synthesis included asymmetric Evans alkylation, ring-closing metathesis reaction, intermolecular amidation, intramolecular aza-Michael addition, and aldol condensation reactions. This strategy may be applied to the total syntheses of this type of natural product.

The first total synthesis of Gardneria oxindole alkaloid (-)-gardmultimine A has been achieved in 19 steps from d-tryptophan in a fully stereocontrolled manner. This synthesis features (1) an Ir-catalyzed regioselective C-H borylation/oxidation sequence to introduce the C12 methoxyl group, (2) a stereocontrolled oxidative rearrangement of indole to construct the spirooxindole motif, and (3) an Au(I)-catalyzed transannular Conia-ene-type 6-exo-dig cyclization to establish the azabicyclo[2.2.2]octane skeleton and the exocyclic E-alkene with exclusive stereoselectivity.

The construction of the ABC tricyclic skeleton of malabanone A with the required 4 stereocenters was accomplished in a concise route starting from R-carvone. The synthesis featured an intramolecular [3 + 2] cycloaddition reaction to assemble its A ring and an intramolecular Diels-Alder reaction to construct its C ring.

A strategy for the synthesis of multisubstituted hydrocarbazoles has been developed through (3 + 2)-annulation of p-quinamines and arynes. In this way, new analogs of hydrocarbazoles with quaternary carbon center can be synthesized in satisfactory yield under mild conditions. Furthermore, this (3 + 2)-annulation can be easily scaled-up, and the products can be modified through simple transformation.

A rapid construction of the tricyclic scaffold of annotinine hydrate has been accomplished in only four steps from conveniently available starting materials. This short synthesis featured an efficient Lewis acid-catalyzed Diels–Alder reaction to construct the 4a, 8a-cis-hydroquinoline skeleton and a 5-exo-trig radical cyclization reaction to assemble the γ-butylrolactone motif.

The first asymmetric total synthesis of the structurally unique Lycopodium alkaloid (-)-lycospidine A, containing an unprecedented five-membered ring, has been accomplished in only 10 steps with 21.6% overall yield from the known conveniently available sulfoxide. This protecting-group-free short synthesis relied on the use of a key amidation/aza-Prins domino cyclization reaction to rapidly construct the tricyclic skeleton and two continuous stereocenters (one of which is a bridged quaternary stereocenter). An intramolecular aldol condensation was successfully utilized to establish the unique five-membered ring, and a late-stage oxidation inspired by biosynthesis pathway was adopted to synthesize the diosphenol ring of (-)-lycospidine A.

A protecting-group-free route for the total synthesis of (-)-lycopodine was demonstrated in only 8 steps from Wade's fawcettimine enone (12 steps from commercial availiable (R)-(+)-pulegone). The key core of this alkaloid was constructed through a phosphoric acid promoted and highly stereocontrolled alkyne aza-Prins cyclization reaction, synchronously establishing the bridged B-ring and the C13 quaternary stereocenter. Importantly, the synthesis further features a new efficient approach for the preparation of other lycopodine-type alkaloids.

The first bioinspired total syntheses of (-) kravanhins A and C were accomplished from a labdane diterpenoid derivative. The key reactions involve a photooxidation and a one-pot sequential aldol cyclization and lactonization, which provide a new plausible biosynthetic pathway for the kravanhins and other symbiotic members.

An efficient method for the 1,3-dipolar cycloaddition of azomethine imines with active esters under thermal conditions has been described in good to high yields. This method offers a straightforward pathway to synthesize bioactive pyrazolidinones.

A sequential reaction combining N-heterocyclic carbene (NHC) and N-hydroxyphthalimide (NHPI) catalysis allowed for the upstream by-product NHPI, which was generated in the NHC-catalyzed cycloaddition reaction, to act as the catalyst for a downstream nitrogen-to-carbon sulfonyl migration reaction. Enantiomeric excess of the major product in the cycloaddition reaction remained intact in the follow-up sulfonyl migration reaction.

An efficient method to build various multisubstituted polycyclic indoline-annulated normal to medium-size rings through dearomatization of indole via a tandem 1,2-acyloxy migration/intramolecular [3 + 2] cycloaddition process is described. The pentacyclic skeleton of strychnine could be synthesized via this tandem cycloaddition and a further Mannich reaction. This approach would provide a novel strategy to the synthesis of strychons alkaloids.

The first asymmetric total synthesis of kravanhin B has been accomplished with a linear reaction sequence of 13 steps starting from (R)-(-)-carvone. The synthesis features an intramolecular aldol cyclization to construct the desired cis-fused decalin skeleton and an acid-catalyzed dehydration and olefin isomerization to install the γ-butenolide ring.

(±)-Aspidospermidine (1) has been synthesized from the commercially available 2,3-dihydro-1H-carbazol-4(9H)-one 6 in 10 steps with 20% overall yield. The key step of the strategy is a one-pot carbonyl reduction/iminium formation/intramolecular conjugate addition reaction that may be applied for the synthesis of other kinds of Aspidosperma alkaloids.

A visible-light-mediated radical addition of alkynoates to generate 3-bromocoumarins by using N-bromosuccinimide as the bromo source has been accomplished. This procedure provides a bromo radical addition/spirocyclization/ester migration cascade reaction under very mild reaction conditions without using any catalyst or strong oxidant and does not need high reaction temperature. Furthermore, the reaction can also be enlarged to the gram scale, and the product 3-bromocoumarins can be further applied in the synthesis of complex compounds.

A cascade reaction to build vinyl cyclobutanol rings through activation of vinyl epoxides by palladium, followed by 1,4-Brook rearrangement and intramolecular cyclization with a palladium complex of the resulting carbon anion, is described. Through this cascade reaction, several highly substituted cyclobutanol substrates were achieved in good yields with high stereoselectivities.

Present methods to synthesize 1,3-dithiane molecules require either harsh reaction conditions or highly specialized reagents. We have developed a catalytic dithioacetalization process that directly gains access to the corresponding 1,3-dithianes using aldehydes and 2-chloro-1,3-dithiane in a highly efficient manner. This methodology is beneficial due to mildness of the reaction conditions, and the dithioacetaliation process results in good to excellent yields by using 15 mol % of an iron catalyst.

Bioinspired total synthesis of gymnothelignan N was accomplished in 13 steps and 6.7% overall yield. The synthesis features a syn Evans aldol reaction, an intramolecular hydrogenative dehydration reaction, and a phenol oxidative dearomatization/Friedel-Crafts reaction, which provides a new plausible biosynthetic pathway for the gymnothelignans and other symbiotic members. Meanwhile, another tetrahydrofuran-type lignan beilschmin A was also synthesized.

An alternative method to an iron-catalyzed radical oxidative cross-coupling reaction followed by 2-chloro-1,3-dithiane and aryl olefins for the synthesis of β-chloro substituent 1,3-dithiane products is presented. The described method has the advantage of mildness of the reaction conditions and tolerates a variety of functional groups. Preliminary mechanistic studies have confirmed the first example of a coupling of 1,3-dithiane with unactivated alkenes that proceeds via an iron-catalyzed oxidative radical intermediate along the reaction pathway.

A concise asymmetric total synthesis of (12S)-12-hydroxymonocerin (1) and (12R)-12-hydroxymonocerin (2) were efficiently achieved from the known 4-bromo-2,6-dimethoxyphenol. The synthetic approach was inspired by our biomimetic synthesis of (+)-monocerin (3) and 7-O-demethylmonocerin (4). The cis-fused furobenzopyranones of 1 and 2 was efficiently constructed via an intramolecular nucleophilic trapping of a quinonemethide intermediate, which was obtained by benzylic oxidation of compound 10 using 2,3-Dichloro-5,6-dicyano-1,4-benzoquinone (DDQ).

A regioselective lateral or vinyl C–H lithiation/1,5-retro-Brook rearrangement via quinolyl or pyridyl ring directed deprotonation has been developed. 16 examples were tested and the corresponding alkyl silanes and E-vinyl silanes were obtained in moderate to good yields.

A regioselective lithiation/retro-Brook rearrangement via direct deprotonation was developed. Varieties of benzyl silanes and vinyl silanes are obtained effectively up to 93% yields.

A visible-light-promoted, mild, and direct difunctionalization of alkynoates has been accomplished. This procedure provides a new strategy toward synthesis of the coumarin core structure by photoredox-mediated oxidation to generate the α-oxo radical, which supervenes a domino radical addition/cyclization reaction in moderate to good yields with high regioselectivity at ambient temperature.

We present the application of a bioinspired collective synthesis strategy in the total syntheses of seven iboga-type indole alkaloids: (±)-tabertinggine, (±)-ibogamine, (±)-ibogaine, (±)-ibogaine hydroxyindolenine, (±)-3-oxoibogaine hydroxyindolenine, (±)-iboluteine, and (±)-ervaoffines D. In particular, tabertinggine and its congeners serve as iboga precursors for the subsequent biomimetic transformations into other iboga-type alkaloids.

An effective synthesis of structurally diverse benzazocines was accomplished in good to excellent chemical yields (55-82 %) through a gold(I)-catalyzed cascade reaction involving tandem 1,2-acyloxy shift/[3+2] cycloaddition of terminal 1,9-enynyl esters. The reaction proceeds under extremely mild conditions and represents one of the relatively few transition-metal-catalyzed intramolecular cycloaddition reactions for the synthesis of benzazocines.

The first total synthesis of the Myrioneuron alkaloids (±)-α,β-myrifabral A and B has been accomplished in only four steps from conveniently available starting materials. This short synthesis relied on the use of a key tandem Mannich/amidation reaction to rapidly construct the core framework and two carbon stereocenters. The synthetic route allows for large scale preparation of these promising natural products against the hepatitis C virus (HCV).

Two down more to go: The asymmetric syntheses of (-)-pentazocine and (-)-eptazocine are presented. The highlights of the syntheses are the construction of the core skeleton through an aza-Prins cyclization and intramolecular Friedel-Crafts reaction.

The angularly fused 6,3,5-tricyclic system is readily generated via a cascade cyclization under acid promotion. The reaction proceeds at room temperature with high stereochemical fidelity from the electrophilic center of the epoxide to the cyclopropane product. This methodology provides a potentially useful approach for the synthesis of mycorrhizin A and its analogues.

Functionalized α-hydroxy carbonyl compounds were prepared from various aldehydes and allylic acetates via a multicomponent reaction, which were catalyzed by N-heterocyclic carbene and Pd catalysts in one pot.

The intramolecular nucleophilic addition reaction of acyl anion equivalents to enol ethers is described, which was catalyzed by N-heterocyclic carbenes generated in situ from readily available thiazolium salt. In this transformation, benzofuranones were obtained in excellent yield. In combination with our previous work, the precise mechanistic elucidation for the formation of benzofuranones has been further investigated. A labeling experiment implied that the transformation proceeds through a nucleophilic addition mechanism.

A mild and efficient method for the deprotection of the TBS and THP ethers is described. A wide variety of TBS ethers as well as THP ethers can be easily deprotected to the corresponding parent hydroxyl compounds by employing a catalytic amount of tris(4-bromophenyl)aminium hexachloroantimonate (TBPA(+center dot)SbCl(6)(-)) in methanol at room temperature in good yield. (C) 2008 Elsevier Ltd. All rights reserved.

An efficient acid-promoted domino Friedel-Crafts (FC) acylation/alkylation reaction has been developed for the construction of the core 6,5,6-ABC tricyclic skeleton of taiwaniaquinoids. The formal total syntheses of diterpenoids (+/-)-taiwaniaquinol B and (+/-)-dichroanone based on this strategy have been achieved.

Carbolithiation of a range of substituted stilbenes and styrenes with dithianyllithiums is described, leading to the rapid, efficient and stereocontrolled assembly of highly functionalized dithiane intermediates for acyl-equivalents synthesis.

The facile total synthesis of the (−)-Heliconol A (ent-1) as well as its diastereoisomer 18 is described, in which different reaction sequences lead to different results. The osmylation of 15 followed by hydrolysis afforded a single isomer 18, otherwise, a mixture of ent-1 and 18 resulted. Other important processes include the catalytic asymmetric CBS reduction and induced osmylation. The synthesis proceeded with a sequence of 11 steps, affording ent-1 in 9.0% and 18 in 22% overall yield, respectively.

The synthesis of heliannuol D along with the first synthesis of heliannuol B has been achieved using Mitsunobu reaction and ring-closing metathesis as the key steps.

A general and efficient route for the synthesis of 5,6- seco -hexahydrodibenzopyran and trans -hexahydrodibenzopyran analogues was established, via a highly regio- and stereoselective S N 2′ reaction of arylcyanocuprates to enol silyl ether of α,β-epoxycyclohexanone. It was applied to the first facile total synthesis of (+)-Machaeridiol B and (+)-Machaeriol B.

The first asymmetric total syntheses of (+)-dihydrolyfoline and (−)-5-epi-dihydrolyfoline have been achieved in five and six steps with 4.6% and 14% overall yields, respectively, in which the chiral biaryl axes were constructed in a highly regioselective and stereoselective manner via a biogenetic enzymatic oxidative couplings of phenols, and the requisite quinolizidinone cores were prepared by an enzymatic Mannich reaction.

A variety of cyclopropane derivatives bearing stereochemistry at all three positions on the ring were readily obtained in a high yield of 76–92% and high stereoselectivity (trans:cis > 95:5) when the monocarboxylic vinyl epoxide analogues reacted with dithianyllithiums in the presence of HMPA. This reaction was supposed to be a tandem conjugation addition-opening epoxide ring sequence.

A mild and efficient method to selectively oxidize chiral sec-1,2-diols has been developed, which demonstrates that 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) can selectively oxidize benzylic or allylic hydroxyl group of sec-1,2-diols under ultrasound wave promotion. The configuration of the adjacent chiral center is retained.

A series of naturally occurring C-7 oxidized abietane diterpenes have been synthesized from racemic ferruginyl methyl ether in high yields. 6-Hydroxyl-5,6-dehydrosugiol (7) can be converted into stable xanthoperol (12) using high temperature. Among the products, the structures of sugiyl methyl ether (2) and 6(-hydroxysugiyl methyl ether (8) were determined by X-ray analysis.

A concise construction of the 6/6/5 tricyclic core of Lycopodium alkaloid palhinine A (1) has been accomplished. The developed synthetic strategy featured a tandem oxidative dearomatization/intramolecular Diels-Alder reaction to construct C/D rings and an intramolecular 5-exo-trig radical cyclization to install the B ring of palhinine A (1). The developed approach paves the way for the total synthesis of palhinine A (1).