Synthesis of methyl (5Z,8Z,10E,12E,14Z)-eicosapentaenoate

The first total synthesis of methyl (5Z,8Z,10E,12E,14Z)-eicosapentaenoate has been achieved in seven steps and in 16% overall yield. The synthesis confirmed the assigned structure of this polyunsaturated natural product.     

Synthesis of N-linked glycan derived from Gram-negative bacterium, Campylobacter jejuni

Recent research has revealed the presence of asparagine (Asn)-linked (N-linked) glycoproteins in certain prokaryotes. In this paper, we describe the chemical synthesis of a novel N-glycan derived from Campylobacter jejuni, a heptasaccharide composed of Asn-linked bacillosamine (Bac), repeating GalNAc, and branching Glc, namely GalNAc-α(1,4)-GalNAc-α(1,4)-[Glc-β(1,3)-]GalNAc-α(1,4)-GalNAc-α(1,4)-GalNAc-α(1,3)-Bac. The synthesis started from a Bac-acceptor, which was consecutively glycosylated with 4-O-pentafluoropropionyl (PFP) protected donors to give heptasaccharide. Reduction of azide groups was followed by debenzylation to complete the synthesis of the target oligosaccharide.     

Synthesis of modified Weinreb amides: N-tert-butoxy-N-methylamides as effective acylating agents

An efficient preparation of N-methyl-O-tert-butylhydroxylamine hydrochloride has been settled, which allowed the synthesis of modified Weinreb amides. Nucleophilic addition of organolithium and Grignard reagents on these N-tert-butoxy-N-methylamides afforded efficiently the corresponding ketones and reduction with DIBAL furnished the corresponding aldehydes in good yields up to 97%.     

Synthesis of N-substituted 1,2,3,4-tetrahydrobenz[g]isoquinoline-5,10-diones

The synthesis of 1,2,3,4-tetrahydrobenz[g]isoquinoline-5,10-dione hydrochlorides is reported starting from 1,4-dihydrobenz[g]isoquinoline-3(2H)-ones or ethyl (3-aminomethyl-1,4-dimethoxynaphth-2-yl)acetates. A third strategy relies on the synthesis of the title compounds via an N-protected 2-(3-bromomethyl-1,4-dimethoxynaphth-2-yl)ethylamine. The synthesized 1,2,3,4-tetrahydro-benz[g]isoquinoline-5,10-diones are a new class of quinones, which have not been reported yet.     

Synthesis of 1,3-disubstituted benzo[c]thiophene analogs containing benzo[b]thiophene/benzo[b]pyrrole

The synthesis of 1,3-disubstituted benzo[c]thiophene analogs incorporating benzo[b]thiophene/benzo[b]pyrrole units is described.     

One-pot approach for the synthesis of 2-aryl benzothiazoles via a two-component coupling of gem-dibromomethylarenes and o-aminothiophenols

One-pot synthesis of 2-aryl benzothiazoles from gem-dibromomethylarenes using 2-aminoarylthiols is described. Benzothiazoles were obtained in high chemical yields under mild conditions. This transformation would facilitate synthesis by short reaction times, large-scale synthesis, easy and quick isolation of the products, which are the main advantages of this procedure.     

Stereoselective synthesis of (+)-(8R,8aR)-perhydro-8-indolizidinol

A highly stereoselective total synthesis of (+)-(8R,8aR)-perhydro-8-indolizidinol is described. Key steps involved in this synthesis are diastereoselective zinc allylation, azido-olefin cyclization and reductive amination followed by cyclization which effectively constructed the indolizidine ring. This contributes a unique approach to the synthesis of indolizidine alkaloids that offers the advantages of brevity and relatively high overall yields.     

One-pot synthesis of 12H-benzo[b]xanthen-12-ones and naphtha[2,3-b]furans from non-naphthalene substrates

An efficient one-pot synthesis of 12H-benzo[b]xanthen-12-ones via an oxidant initiated and base promoted tandem reaction of 2-(4-(2-haloaryl)-4-hydroxybut-1-ynyl)benzaldehydes has been developed. By using similar strategy, a one-pot synthesis of naphtha[2,3-b]furans from the cascade reaction of 2-(4-hydroxy-but-1-ynyl)benzaldehydes with 2-bromoacetonitrile or α-bromocarbonyl compounds has also been achieved.     

Concise total synthesis of flavone C-glycoside having potent anti-inflammatory activity

The total synthesis of anti-inflammatory active flavone C-glycoside isolated from oolong tea extract is achieved. Introducing a C-glucosyl moiety to an aryl system and constructing a fused tetracyclic ring characteristic to this natural product were conducted based on the O-to-C rearrangement of sugar moiety and the successive intramolecular Mitsunobu reaction, respectively. This concise and efficient synthetic pathway is applicable to the large-scale synthesis of target flavone and for constructing a large library of related compounds.     

A total synthesis of (R,S)S-glucoraphanin

A total synthesis of (R,S)_S-glucoraphanin (GRP) has been completed by a novel, simple and convenient method in high overall yield (17% over seven steps). The study describes a method for the synthesis of natural and unnatural (methylsulfinyl)alkyl glucosinolates (GLs) and also opens useful pathways to synthesize GRP as well as other sulfinyl GLs.     

Efficient one-pot trans-dihydroxylation of 2H-pyrans using dimethyldioxirane (DMD): synthesis of trans-3,4-dihydroxy-3,4-dihydro-O-methyloctandreolones, orixalone D, and trans-3,4-dihydroxy-3,4-dihydromollugin natural products

An efficient one-pot formation of trans-diols on 2H-pyranyl rings was achieved by dimethyldioxirane in wet acetone. This new methodology was applied to the synthesis of natural products containing trans-diol on the pyranyl rings such as trans-3,4-dihydroxy-3,4-dihydro-O-methyloctandreolones, orixalone D, and trans-3,4-dihydroxy-3,4-dihydromollugin.     

The fragmentation reaction of 16R-bromopregnane-3S,20S-diol

16R-Bromopregnane-3S,20S-diol reacted with potassium t-butoxide to afford androst-16-en-3S-ol in a moderate yield via fragmentation reaction. The latter is a key intermediate for the synthesis of 5α-androst-16-en-3-one, as boar sex pheromone, and other steroidal drugs. In addition, 16R,20S-epoxypregnane-3S-ol was also obtained as a major product by changing the reaction solvent.     

One-pot synthesis of benzimidazoles from gem-dibromomethylarenes using o-diaminoarenes

A one-pot synthesis of benzimidazoles from gem-dibromomethylarenes is described. The reaction shows the method to prepare a variety of benzimidazole analogues with excellent yield.     

A convenient and efficient synthesis of (S)-lysine and (S)-arginine homologues via olefin cross-metathesis

A convenient five step synthesis of (S)-homolysine, incorporating a key olefin cross-metathesis step in the chain extension methodology, has been developed, together with a six step related synthesis of a new homologue of arginine, (S)-bishomoarginine.     

One pot conversion of azido arenes to N-arylacetamides and N-arylformamides: synthesis of 1,4-benzodiazepine-2,5-diones and fused [2,1-b]quinazolinones

Sodium iodide in acidic media has been employed for the synthesis of N-arylformamides and N-arylacetamides. The NaI/acetic acid reagent system has also been extended for the synthesis of 1,4-benzodiazepine-2,5-diones, pyrrolo[2,1-c][1,4]benzodiazepine-5,11-diones, and fused [2,1-b]quinazolinones.     

Synthesis and evaluation of N6-substituted azide- and alkyne-bearing N-mustard analogs of S-adenosyl-l-methionine

The synthesis of a family of N-mustard analogs of S-adenosyl-l-methionine (SAM) containing azides and alkynes at the N6-position of the adenosine base has been accomplished from commercially available inosine. Further biochemical analysis of these analogs indicates successful modification of pUC19 plasmid DNA in an enzyme-dependent fashion with DNA methyltransferases M.TaqI and M.HhaI.     

Vinylogous N,N-dimethylaminomethylenation of 3-[(1-substituted)ethylidene]-oxindoles with N,N-dimethylformamide dimethylacetal

An efficient stereoselective synthesis of various 3-(3-dimethylaminoprop-2-enylidene)oxindoles has been disclosed. The compounds were synthesized via a vinylogous N,N-dimethylaminomethylenation at the γ-position of 3-[(1-substituted)ethylidene]oxindoles with DMF-DMA.     

Synthesis of meso-tetraphenyl porphyrins via condensation of dipyrromethanes with N-tosyl imines

A new synthetic route for the synthesis of 5,10,15,20-tetraphenyl porphyrins has been developed based on the reaction of 5-substituted dipyrromethanes with N-tosyl imines in the presence of a metal triflate catalyst. meso-Substituted tetraphenyl porphyrins were synthesized in a two-step process. The first step of the method is the metal triflate-catalyzed condensation of 5-substituted dipyrromethanes with N-tosyl imines to form a porphyrinogen intermediate and the second step is the oxidation of the porphyrinogen to porphyrin. The method was applied to the synthesis of trans-A₂B₂-tetraarylporphyrins and the products were obtained with only a trace amount of one scrambling product. The synthesis of two important building blocks for porphyrin synthesis, mono and di-sulfonamide alkylated 5-substituted dipyrromethanes, was achieved by the addition of 5-substituted dipyrromethane to N-tosyl imine. The application of mono and di-sulfonamide alkylated 5-substituted dipyrromethanes in ‘2+2’ porphyrin formation reactions is presented.     

Efficient iodine catalyzed chemoselective synthesis of aminals—an access to N,N-acetals by the addition of lactams to N-acyl imines

A highly efficient protocol has been developed for the synthesis of aminals from γ-butyrolactam and benzaldehyde using iodine as Lewis acid catalyst. The attack of γ-butyrolactam nucleophile to intermediate N-acyliminium ion was more favorable, when aryl aldehyde bears the electron donating group (EDG). Iodine plays a key role in these reaction transformations. This current mild protocol is environmentally benign and cost-effective method for the synthesis of industrially and pharmaceutically useful scaffolds.     

Investigation towards an efficient synthesis of benzo[g]isoquinoline-1,5,10(2H)-triones

As part of our research on 2-aza analogues of pentalongin, the active principle of Pentas longiflora Oliv., the first synthesis of 2,3-disubstituted benzo[g]isoquinoline-1,5,10(2H)-triones via 3,4-disubstituted 6-hydroxybenzo[g]furo[4,3,2-de]isoquinoline-2,5(4H)-diones as the key intermediates is reported. The latter compounds have been prepared by treating 2-methoxycarbonyl-1,4-naphthoquinone with N-substituted enaminoesters under acidic conditions. These reagents are easily accessible from readily available 1,4-dihydroxy-2-naphthoic acid, β-ketoesters and primary amines. Finally, a short synthesis of substituted benzo[g]isoquinoline-1,5,10(2H)-triones is achieved by an oxidative addition of N-substituted enaminoesters onto methyl 1,4-dihydroxynaphthalene-2-carboxylate.