Concise total syntheses of variolin B and deoxyvariolin B

The total synthesis of the marine alkaloid variolin B has been achieved in 8 steps and 17% overall yield, starting from commercially available 4-chloro-2-methylthiopyrimidine. The key reaction involves the tandem deoxygenation and cyclization of a triarylmethanol using a combination of triethylsilane and trifluoroacetic acid. In addition, the deoxygenated analogue was prepared in 6 steps and 23% overall yield, starting from the same starting material.     

Concise total syntheses of heliannuols B and D

Concise and efficient enantioselective total syntheses of heliannuols B and D have been accomplished using chirality transfer through a Lewis acid-promoted Claisen rearrangement for the construction of the C7 tertiary stereogenic center and a relay ring-closing metathesis for assembling the dihydrobenzo[b]oxepine backbone of the natural products as the key steps.     

Concise, protecting group free total syntheses of (+)-sattabacin and (+)-4-hydroxysattabacin

The first asymmetric total syntheses of the antiviral natural products (+)-sattabacin and (+)-4-hydroxysattabacin are reported. Both total syntheses are remarkably concise and were completed without the use of protecting groups. These syntheses allowed the unambiguous assignment of the absolute configuration of both natural products. The syntheses of these natural products, which exhibit marked antiviral activity, are readily amenable to the preparation of structural analogs and progress in this regard is also reported.     

Concise enantiospecific, stereoselective syntheses of (+)-crispine A and its (-)-antipode

An enantiospecific and stereoselective total synthesis of the natural product (+)-crispine A has been demonstrated employing a Pictet-Spengler bis-cyclization reaction between commercially available (R)-(-)-methyl 2-amino-3-(3,4-dimethoxyphenyl)propanoate and 4-chloro-1,1-dimethoxybutane to preferentially provide the cis tricyclic adduct. Decarboxylation by a convenient two-step protocol provided the enantiopure natural product in three steps with an overall isolated yield of 32% from the amino acid. The unnatural antipode (-)-crispine A was similarly prepared in three steps from the commercially available (S)-(+)-amino acid.     

Concise enantioselective syntheses of quinolactacins A and B through alternative Winterfeldt oxidation

Enantioselective total syntheses of (+)-quinolactacin B and (+)-quinolactacin A2 through asymmetric Pictet-Spengler cyclization and KO(2) oxidation-an alternative Winterfeldt condition-are described.     

Concise syntheses of cystothiazoles A, C, D, and melithiazol B

A convergent synthesis of cystothiazoles C 1 and D 3 was achieved based on Julia coupling between the functionalized aldehyde 5b, corresponding to left half of the final molecule, and aryl sulfone 6 or 7, bearing a bithiazole moiety, corresponding to right half. Methylation of 1 and 3 gave cystothiazole A 2 and melithiazol B 4, respectively. The overall yield (5 steps from (2R,3S)-3-methylpent-4-yne-1,2-diol 10; 57%) of 5b via the present route was improved in comparison to that of the previously reported functionalized aldehyde 5a (7 steps from 10; 13%). By applying the modified Julia coupling method, selectivity (6E/6Z=20 : 1-26 : 1) toward the (6E)-form of the coupled products (15 or 19) against the corresponding (6Z)-form was improved in comparison to the Wittig method (6E/6Z=4 : 1-6.9 : 1).     

Concise syntheses of (+)- and (−)-methylenolactocins and phaseolinic acids

(+)- and (−)-Methylenolactocins and phaseolinic acids are synthesized in four steps via asymmetric syn- and anti-aldol reactions of chiral N-succinyl-2-oxazolidinones using the same set of reagents.     

Concise enantioselective total syntheses of (+)-homochelidonine, (+)-chelamidine, (+)-chelidonine, (+)-chelamine and (+)-norchelidonine by a Pd II-catalyzed ring-opening strategy

New enantioselective syntheses of the B/C hexahydrobenzo[c]phenanthridine alkaloids (+)-homochelidonine, (+)-chelamidine, (+)-chelidonine, (+)-chelamine, and (+)-norchelidonine are described. Our rapid and convergent route to this class of natural products involved the development and application of a Pd II-catalyzed asymmetric ring-opening reaction of a meso-azabicyclic alkene with an aryl boronic acid as the key step. By screening a variety of functionalized ortho-substituted aryl boronic acids, chiral ligands and reaction conditions we were able to prepare the requisite cis-1-amino-2-aryldihydronaphthalenes in high yield and in up to 90 % ee. Early attempts to complete the synthesis of (+)-homochelidonine using an N-Boc azabicyclic alkene are described in full. The successful route required a protecting group alteration followed by B ring formation and then stereoselective installation of the C-11 syn-hydroxy group by regioselective epoxide ring-opening using a hydride source. Ring-opening of the same epoxide intermediate with water ultimately led to the synthesis of (+)-chelamidine. The same strategy was then used to synthesize the other structurally similar B/C hexahydrobenzo[c]phenanthridine alkaloids, (+)-chelidonine, (+)-chelamidine, and (+)-norchelidonine.     

Concise synthesis of (+)-serinolamide A

Serinolamide A, isolated from a species of marine cyanobacteria, exhibits a moderate agonist effect and selectivity for the CB₁ cannabinoid receptor, which is unusual for marine natural products. Herein, we reported a highly efficient enantiospecific first total synthesis of (+)-serinolamide A from l-serine in nine steps with 30% overall yield. The synthesis method provides a facile, practicable, and economical approach for the preparation of other similar endocanabinoid lipids.     

Concise syntheses of (+)-austrodoral and (+)-austrodoric acid Based on H2O2 mediated oxidative ring contraction

Asymmetric synthesis of the marine nor-sesquiterpenoid (+)-austrodoric acid and (+)-austrodoral in seven and nine steps respectively from Wieland-Miescher ketone was described herein. The synthesis featured an oxidative ring contraction of α-formyl cyclic ketone mediated by H₂O₂ to forge the hydrindane scaffold together with the contiguous quaternary carbon centers simultaneously.     

A Concise Route to (+)-Estrone

A concise route to the Torgov diene, the key intermediate of estrone, has been devised using a chiral dioxycyclopentenone as the starting material by employing a sequence of five steps of reactions involving a Lewis acid-mediated Diels-Alder reaction with Dane's diene.     

一种简洁的(+)-新黄皮酰胺的全合成

从化合物5出发,首先通过C-3位羟基的转位反应制得(+)-新黄皮酰胺(1)的前体化合物4,然后经过酮羰基的还原反应合成得到(+)-新黄皮酰胺(1).提供了一种简洁的(+)-新黄皮酰胺的全合成路线.考察了化合物5中C-3位羟基的转位反应的实验条件.     

Concise formal synthesis of (+)-pyripyropene A

A concise enantioselective synthesis of A/B bicyclic segment of naturally occurring α-pyrone meroterpenoid pyripyropene A is achieved in 9 steps (LLS) and 7.5% yield starting from R-(?)-carvone. The significant points of the synthesis include: (1) an intramolecular 1, 3-dipolar cycloaddition reaction to construct the A ring and assemble C4 quaternary carbon stereocenter as well; (2) reductive cleavage of the oxazole motif utilized Raney Ni/B(OCH₃)₃.     

Concise syntheses of racemic and enantiopure deoxydysibetaine

Racemic deoxydysibetaine was efficiently obtained in few steps from methyl pyroglutamate. The 2S enantiomer was synthesized from (S)-pyroglutaminol as chiral starting material, through the key intermediate (S)-2-hydroxymethylglutamic acid recently prepared with complete stereoselectivity in our laboratory.     

Enantioselective syntheses of (+)-xylarenal A and ent-xylarenal A

[reaction: see text] The total synthesis of the sesquiterpenoid xylarenal A is reported. This first synthetic entry to an eremophilane terpenoid with an exocyclic vinyl aldehyde unit involves the use of the bicyclic enone (+)-3, which after a gamma-oxidation and alpha'-allylation leads to the formation of the ketone (+)-8. After its acylation, an oxidative cleavage of the allyl side chain followed by alpha-methylenation of the resulting aldehyde gives (+)-xylarenal A (1). The synthesis of (-)-xylarenal A from (-)-3 is also reported. Moreover, the first total synthesis of the trinoreremophilane (+)-1alpha-hydroxyisoondetianone (5) is described.     

A Concise Total Synthesis of S-(+)-Tylophorine

Phenanthroindolizidine alkaloids, which exhibit extensively biological properties, are widely present at various plants of the Asclepiadaceae family.[1] The significantly biological importance of these natural products has attracted considerable synthetic efforts.[2] We herein report an efficiently asyinmetric synthesis of S-(+)-tylophorine (1), as a typically representative alkaloids.     

A Concise Total Synthesis of S-（＋）-Tylophorine

A highly efficient total synthesis of S-( )-tylophorine has been accomplished in fully asymmetric fashion.     

Total syntheses of (+)-castanospermine and (+)-deoxynojirimycin

The absolute configuration of castanospermine has been determined by total synthesis to be as shown in 1.     

The syntheses of rac-inthomycin A, (+)-inthomycin B and (+)-inthomycin C using a unified synthetic approach

The Stille coupling between a common oxazole vinyl iodide and stereodefined stannyl-diene units is described as the cornerstone of a unified synthetic route to the inthomycin family of bioactive Streptomyces metabolites. This procedure has been utilised to prepare (+)-inthomycin B and (+)-inthomycin C for the first time; in these examples the stereogenic centre was introduced using the Kiyooka ketene acetal/amino acid-derived oxazaborolidinone variant of the Mukaiyama aldol reaction. In addition, a convenient preparation of rac-inthomycin A is described based on the same strategy.