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A general approach for a collective synthesis of natural products containing substituted THF ring is described. In this paper, Arbusculone, a small molecule natural product accomplished using a short route, is used as the key intermediate to achieve the total synthesis of Andirolactone, Pinnatolide, Ipomolactone, Cyclocapitelline, Isocyclocapitelline and their two isomers in less than ten steps. The present effort highlights protecting-group-free total syntheses and the shortest route to access these natural products from commercially available cheap starting materials.

We have developed a facile and efficient synthetic route to substituted isochromans for the first time by reacting 2-(2-bromoethyl)benzaldehyde with a variety of aryl, heteroaryl amines in AcOH. The reaction is catalyst/additive free and takes place at reflux conditions with short reaction time to furnish products in good to excellent yields. All the compounds have been characterized by spectral techniques such as IR, 1H NMR and Mass etc. Synthesized compounds were evaluated for antimicrobial activity against specific bacterial like 1) Staphylococcus strains aureus 2) Bacillus subtilis 3) Escherichia coli 4) Pseudomonas aeruginosa. Compounds 3e, 3n, 3 m, 3 l, 3 k, 3j and 3b showed most potent in vitro activity against bacterial strains.

An efficient and stereoselective approach for the formal total synthesis of Stigmatellin A has been described. The key steps involved in this synthesis are desymmetrization of the bicyclic olefin to introduce two methyl and two hydroxyl chiral centers, Friedel Crafts acylation, regioselective demethylation, Baker-Venkataraman rearrangement and Grubbs cross metathesis.

A first stereoselective total synthesis of 14-memebered β-resorcylic macrolactone 5′-hydroxyzearalenone (1) has been achieved. The key steps are Jocobsen hydrolytic kinetic resolution, Sharpless asymmetric dihydroxylation, Vilsmeier-Haack reaction, Mitsunobu esterification and ring-closing metathesis.

Total synthesis of spiroketal EBC-23 has been described by two divergent approaches from three simple building blocks. Gold-catalyzed cycloisomerization of alkynol and acid-mediated spirocyclization of diketalketone were successfully utilized to effect spiroketal formation. A Cu(I)-P(Cy)3-catalyzed protocol for the highly regio- and stereocontrolled hydroboration of internal propargylic alcohol was effectively applied toward the β-hydroxy ketone via vinylboronates.

The first stereoselective total synthesis of nonenolide (−)-stagonolide D has been accomplished. Midland Alpine borane reduction to install hydroxyl group at C4, Henbest epoxidation to introduce epoxide stereoselectively between C7 and C8, Yamaguchi esterification and Olefin metathesis reaction are the key steps involved in the total synthesis.

An intramolecular annulation strategy has been developed for the synthesis of tetrahydrobenzo[e]pyrano[4,3-c][1,2]thiazine derivatives by means of coupling of aldehydes with 2-(4-hydroxybut-1-yn-1-yl)-N-arylsulfonamides using a catalytic amount of silver hexafluoroantimonate in toluene at 80 °C. This is the first report on the synthesis of fused benzo-δ-sultam derivatives through C–N, C–O, and C–C bond formations. The reaction proceeds through a cascade of hydroamination and Prins type cyclization.

A convergent and stereoselective approach for the synthesis of C1–C23 and C24–C32 segments of polyether antibiotic, ionomycin has been achieved. The key steps involved in this approach are the elaboration of two advanced fragments from a common precursor using enzymatic desymmetrization to create two methyl chiral centers, desymmetrization of the bicyclic olefin to introduce two methyl and two hydroxyl chiral centers, the use of Evans auxiliary to introduce another methyl group and the creation of four chiral centers in bis -tetrahydrofuran ring by Sharpless asymmetric epoxidation and the regioselective opening of epoxide with methyl sulphone. The coupling of C11–C16 with C17–C23 was achieved through a Julia-Kocienski olefination and directed Aldol reaction. Oxidation of C9 alcohol facilitates the coupling of C10–C23 with C1–C9.

A straightforward synthesis of (S)-gingerols 1–3 has been described. The requisite stereogenic center in the target molecules was introduced by Sharpless asymmetric dihydroxylation using a chiral complex, AD-mix β. This route is simple and efficient to prepare the products in very good yields.

A convergent total synthesis of isocladosporin and 3- epi -isocladosporin is reported starting from commercially available homoallyl alcohol in 10 longest linear steps with 28% overall yield. The key steps involved in the synthesis are cross-metathesis, tandem isomerization followed by C O and C C bond formation reactions for the synthesis of trans -2,6-disubstituted dihydropyrans developed by us, acylation reaction and Luche reaction.

A stereoselective synthesis of tetrahydropyran–tetrahydrofuran (THP–THF) core 2 of (+)-muconin (1) has been achieved using Prins cyclization as a key step to construct tetrahydropyran moiety. Other important transformations such as Wittig olefination, Sharpless epoxidation, regio-, and stereoselective exo-cyclization of the epoxy alcohol, titanocene induced regioselective deoxygenation of 2,3-epoxy alcohol, Grignard reaction, and Barton–McCombie reaction are successfully employed to accomplish the synthesis of THP–THF core 2.

Stereoselective synthesis of the C21–C40 core segment of caylobolide A has been achieved following a highly efficient convergent strategy. The key reactions featured in the synthesis are Prins cyclization, reductive radical cyclization, Sharpless asymmetric epoxidation and olefin cross metathesis.

The stereoselective synthesis of C1-C17 fragment of salinomycin is achieved. The strategy employs a desymmetrization approach and utilizes an intramolecular oxetane opening reaction with O-nucleophile to result in the tetrahydropyran skeleton as the key step.

The synthesis of phomopsolide B has been achieved using an olefin cross-metathesis (CM) reaction as key step. Two metathesis partners, enediol and 5-hydroxy vinyl lactone were prepared from l -ascorbic acid. This is the first report of using 5-hydroxy vinyl lactone in an olefin cross-metathesis reaction.

An asymmetric synthesis of spiroketal fragment of an antitumour antibiotic, ossamycin is described. Coupling of aldehyde and alkyne fragments followed by spiroketalization has afforded the spiroketal sub unit of ossamycin. Both the sub targets were constructed via Prins cyclization.

A concise approach for the total synthesis of attenols A and B is described involving MacMillan’s α-aminooxylation, Evan’s asymmetric alkylation, Brown’s allylation, and spiro-ketalization as key steps. This approach has successfully demonstrated the α-aminooxylation protocol for the construction of the anti-1,3-diol unit.

The stereoselective total synthesis of (−)-brevisamide, a novel marine cyclic ether alkaloid isolated from dinoflagellate karenia brevis is described. The key steps involved in this synthesis are the Sharpless asymmetric epoxidation and regioselective ring opening of chiral epoxide by Gilman's reagent. The tetrahydropyran core has been constructed by an intramolecular SN2 cyclisation.

A bioglycerol derived carbon-sulfonic acid is found to catalyze efficiently the three-component one-pot condensation of isatin, malononitrile, and 1,3-dicarbonyls to afford a wide range of spiro[4H-pyran-3,3′-oxindole]derivatives in good yields and selectivity. The use of a recyclable solid acid catalyst makes this method simple, convenient, and cost-effective.

The asymmetric and convergent synthesis of fully functionalized macrocyclic core of tulearin C is described. Sharpless asymmetric epoxidation, Gillman’s reaction, olefin cross metathesis, α aminoxylation, and ring closing metathesis reactions are the key steps utilized in the synthesis of macrolactone.

A novel Prins/Friedel–Crafts cyclization of ( Z )-6-(1-methyl-1 H -indol-3-yl)hex-3-en-1-ol with aldehydes has been achieved using a catalytic amount of BF 3 ·OEt 2 under mild reaction conditions to produce the corresponding octahydropyrano[4,3- a ]carbazole derivatives in good yields with high diastereoselectivity. The cross-coupling of ( Z )-6-(1-methyl-1 H -indol-3-yl)hex-3-ene-1-thiol with aldehydes affords the corresponding octahydrothiopyrano[4,3- a ]carbazole derivatives under similar conditions.

The homoallylic alcohol tethered with a benzylic hydroxyl group, that is, ( E )-4-(2-(hydroxymethyl)phenyl)but-3-en-1-ol undergoes smooth Prins bicyclization with various aldehydes in the presence of 20 mol % Sc(OTf) 3 and 4 A MS at 80 °C to afford a novel series of 1-(tetrahydrofuran-3-yl)-1,3-dihydroisobenzofuran derivatives in good yields with high diastereoselectivity.

Excess molar volumes V E, excess molar enthalpies H E, and speeds of sound u for 1-methyl pyrrolidin-2-one (1) + water or propan-1-ol or propan-2-ol (2) binary mixtures have been measured over the entire composition range (at 308.15 K) using a dilatometer, calorimeter and interferometer. Speeds of sound data, u, of (1 + 2) binary mixtures have been utilized to determine excess isentropic compressibilities, $$ \kappa_{S}^{\text{E}} $$ . The observed V E, H E and $$ \kappa_{S}^{\text{E}} $$ data have been analyzed in terms of (1) Graph theory (which involves the topology of the constituents of mixture), and (2) the Prigogine–Flory–Patterson theory. Analysis of V E data in terms of Graph theory suggests that 1-methyl pyrrolidin-2-one, water, propan-1-ol, and propan-2-ol exist as associated molecular entities. IR studies lend additional support to the proposed molecular entities in (1 + 2) mixtures. It has been observed that V E, H E and $$ \kappa_{S}^{\text{E}} $$ values predicted by Graph theory compare well with their corresponding experimental values.

A novel method has been devised for the synthesis of 2,4,5-trisubstituted pyrrole derivatives through the coupling of α-diazoketones with β-enaminoketones and esters using 10 mol % of Cu(OTf)(2). A wide range of 2,3-disubstituted indole derivatives were also prepared from α-diazoketones and 2-aminoaryl or alkyl ketones. The synthetic versatility of this approach has been exemplified in the formal synthesis of homofascaplysin C.

The stereoselective synthesis of C1–C10 fragment of cytostatic macrolide bryostatin is described. Two of the three chiral centers have been established via the Sharpless kinetic resolution of racemic allylic alcohol 15 followed by regioselective reduction of epoxy alcohol 8 with Red-Al. Diastereoselective Aldol reaction of an aldehyde 7 with methyl isobutyrate affords the corresponding β-hydroxyester 23 which is then transformed into tetrahydropyran ring system 3 via an intramolecular hemi-ketalization.

1-Aryl-3,4-dihydroisoquinolines undergo smooth acetoxylation/alkoxylation in the presence of 5 mol % Pd(OAc)2 and a stoichiometric amount of PhI(OAc)2 by means of C–H activation to produce the corresponding acetoxy- and alkoxy-1-aryl-3,4-dihydroisoquinoline derivatives respectively in good yields with high regioselectivity. It is a first example on oxidative functionalization of arenes tethered to dihydroisoquinoline moiety via the C–H activation.

A highly stereoselective approach to the total synthesis of seimatopolide A and (2 S ,3 R ,5 S )-(−)-2,3-dihydroxytetradecan-5-olide is described via a common polyketide precursor by means of Prins reaction and MacMillan aminoxylation sequence.

A concise total synthesis of (+)-deoxocassine ( 1 ) and (−)-deoxoprosophylline ( 2 ) has been achieved for the first time from d -xylose. The key steps involved in these synthesis are alkyl Grignard reaction, S N 2 substitution of mesylate by azide, Wittig reaction, and reductive amination.

An intramolecular Ugi reaction of 2-(2-formyl-1H-indol-1-yl)acetic acid with aryl amines and isocyanides has been developed to produce a novel class of N-alkyl-3-oxo-2-aryl-1,2,3,4-tetrahydropyrazino[1,2-a]indole-1-carboxamides in good yields. This is the first report on intramolecular Ugi three component reaction of 2-(2-formyl-1H-indol-1-yl)acetic acid, aryl amine, and isonitrile.

A variety of aldehydes undergo a tandem acetalization and intramolecular Prins cyclization with pent-4-ene-1,2-diol in the presence of 5 mol % scandium triflate and 15 mol % p-toluenesulfonic acid (TsOH) in dichloroethane at 80 °C to produce the corresponding bicyclic ethers, that is, 2,6-dioxabicyclo[3,2,1]octane derivatives in good yields and with high selectivity. The salient features of this methodology are higher yields, lower catalyst loadings, and faster reaction times. The combination of Sc(OTf)3 and TsOH (1:3) was found to be more effective than either Sc(OTf)3 or TsOH alone.

Stereoselective synthesis of the C38–C54 segment of a marine metabolite halichondrin B comprising KLM and N rings with a C44 spiroketal including 10 chiral centers is described. The salient features of the synthesis are Carreira’s addition, Sharpless asymmetric dihydroxylation and double alkylation of TosMIC strategy and double vinyl coupling reactions.

A tandem cycloisomerization/Friedel–Crafts alkylation of indoles has been achieved in a one-pot process to produce 2,5-disubstituted furans using gallium-catalyzed sequential nucleophilic addition onto metal-activated 1-alkynyl-2,3-epoxy acetates. The reaction proceeds efficiently under mild conditions with complete regioselectivity to afford the substituted furan derivatives in good yields with high diversity.

(2-(4-Methoxyphenyl)-4-methylenetetrahydrofuran-3-yl)methanol reacts smoothly with different aldehydes in the presence of InCl 3 at an ambient temperature to afford a novel series of cis -fused 7a,3,6-trisubstituted hexahydro-1 H -furo[3,4- c ]pyran derivatives in good yields with high selectivity. This is the first Letter on the synthesis of cis -fused hexahydro-1 H -furo[3,4- c ]pyran derivatives via the Prins cyclization.

The furan-2-yl(phenyl)methanol undergoes smooth aza-Piancatelli rearrangement with aryl amines in the presence of 0.03 mol % phosphomolybdic acid in acetonitrile under reflux conditions to afford the corresponding trans -4,5-disubstituted cyclopentenone derivatives in good yields with high selectivity in short reaction time.

A tandem ene/Prins cyclization of olefin tethered aldehyde with an aldehyde has been accomplished using 5 mol % scandium triflate at ambient temperature to afford a novel series of cis-fused octahydropyrano[2,3-c]pyrrole derivatives in good yields with high selectivity. This is the first report on a tandem cyclization of 4-methyl-N-(3-methylbut-2-enyl)-N-(2-oxoethyl)benzenesulfonamide with aldehydes.

A stereoselective synthesis of fragment A of cryptophycin is achieved utilizing the versatile Prins cyclization. Subsequently, the total synthesis of cryptophycin-24 (arenastatin A) has been accomplished by coupling it with the depsipeptide subunit.

Indium(III) bromide has been used for the first time for the synthesis of imidazo[1,2-a]pyridines in a one-pot operation from 2-aminopyridine, aldehydes, and alkynes. InBr3 was found to be more effective for the activation of both alkyne and imine derived from aryl aldehyde and 2-aminopyridine.

A highly regioselective ortho-acetoxylation of N-(2-benzoylphenyl)benzamides has been achieved using a catalytic amount of Pd(OAc)2 (10 mol %) and a stoichiometric amount of PhI(OAc)2 in a mixture of acetic anhydride and acetic acid via C–H activation to produce the corresponding 2-acetoxybenzamides in good yields. ortho-Methoxylation has been accomplished using methanol under similar conditions.

Highly stereoselective total syntheses of polyrhacitide A and epi-cryptocaryolone have been achieved in 11 steps with high overall yield of 24% and 28%, respectively, following a recently developed strategy for the construction of trans-2,6-disubstituted-3,4-dihydropyrans. In this report, the versatility of iodo-cyclization for the total syntheses of polyrhacitide A and epi-cryptocaryolone is demonstrated.

A three-component, four-center Ugi reaction has been developed to produce a novel class of 2-aryl-3-oxo-hexahydroazepino[3,4-b]indole and 2-aryl-3-oxo-tetrahydro-1H-pyrido[3,4-b]indole derivatives in good to high yields. A few of them exhibit moderate cytotoxicity against various cancer cell lines such as HeLa (human epithelial cervical cancer), A549 (human lung carcinoma epithelial), DU145 (human prostate carcinoma epithelial) and MCF-7 (human breast adenocarcinoma).

A stereoselective total synthesis of oplopandiol, oploxyne A, and (−)-oploxyne B is described. The key reactions include Sharpless asymmetric epoxidation, d -proline catalyzed aminoxylation, Cadiot–Chodkiewicz cross-coupling reaction, m- CPBA induced substrate-controlled stereoselective epoxidation, and Lewis acid catalyzed stereo- and regioselective ring-opening of epoxide.

A convergent synthesis of C19–C27 fragment (2) of bryostatin-11 is described. The key steps involved in this approach are kinetic resolution, Grignard reaction, and Sharpless dihydroxylation. AIBN catalyzed radical cyclization strategy has been used for the first time to construct the six-membered pyran system.

A concise and efficient total synthesis of honokiol, a biphenyl-type neolignan is accomplished in six steps using readily available and cost-effective reagents. The synthetic route involves mainly the Grignard reaction, iodine mediated aromatization, and Claisen rearrangement as key steps. A predominant formation of honokiol (1a) was observed in the Claisen rearrangement under microwave irradiation whereas the isohonokiol (1b) was formed as a major product under conventional conditions.

1,3-Diaryl propargyl alcohols undergo smooth intramolecular Friedel-Crafts cyclization with triethylsilane in the presence of 10 mol % iodine 3-aryl-1H-indene derivatives in good yields in short reaction times. This is the first example on the synthesis of substituted indenes from 1,3-diaryl propargyl alcohols. The use of inexpensive and readily available molecular iodine makes this method quite simple, more convenient, and practical.

( R )-Citronellal undergoes initial ene reaction followed by Prins cyclization with aldehydes in the presence of 5 mol % of scandium triflate at ambient temperature to furnish octahydro-2 H -chromen-4-ols in good yields and with high cis -selectivity. The use of scandium triflate makes this procedure simple, more convenient, and practical.

The coupling of (E)- and (Z)-hex-3-ene-1,6-ditosylamide with various aldehydes in the presence of 10 mol % Sc(OTf)3 gave the corresponding trans- and cis-fused 1,5-ditosyl-octahydro-1H-pyrrolo[3,2-c]pyridines, respectively, in good yields via intramolecular aza-Prins cyclization, whereas the coupling of (E)- and (Z)-N-(6-hydroxyhex-3-enyl)-4-methylbenzenesulfonamide afforded the corresponding trans- and cis-fused octahydro-1-tosylpyrano[4,3-b]pyrroles derivatives, respectively, via intramolecular Prins-cyclization.

Indoles undergo smooth alkylation with α- and β-pinenes in the presence of 20 mol % of anhydrous FeCl 3 under mild reaction conditions to produce a wide range of the corresponding 3-alkylated indoles in excellent yields with high trans-selectivity. This is the first example of alkylation of indoles with mono-terpenes.

Indium(III) bromide has been used for the first time for the synthesis of propargyl amines in a one-pot operation from aldehydes, amines and alkynes.

Ketones undergo smooth rearrangement with TMSN3 in the presence of FeCl3 under extremely mild conditions to provide the corresponding amides, imides and lactams in good yields with high selectivity. This method is very useful for the preparation of a wide range of amides, imides and lactams from ketones. The use of FeCl3 makes this method simple, convenient and cost-effective.

2-Deoxyribose, an aryl amine and acetyl acetone undergo smooth cyclocondensation in the presence of 10 mol % of InCl 3 under mild conditions to afford the corresponding sugar-derived bicyclic aminols in good yields with moderate diastereoselectivity. This reaction is reminiscent of the celebrated tropinone synthesis of Robinson. The structures of the products are established by using various NMR experiments and X-ray crystallographic studies.

Indoles undergo smooth alkylation at the 3-position with 1,3-dicarbonyl compounds in the presence of 20 mol % of FeCl3 under mild reaction conditions to produce a wide range of 3-substituted indoles in excellent yields and with high E-selectivity.