A short synthesis of koniamborine, a naturally occurring pyrano[3,2-b]indole

An expedient synthesis of the alkaloid koniamborine, the only to date isolated naturally occurring pyrano[3,2-b]indole is presented. The key pyrano[3,2-b]indole forming step is a palladium-catalyzed reductive N-heteroannulation of 2-(4-methoxy-2-nitrophenyl)-(4H)-pyrane-4-one.     

An expedient synthesis of orthogonally protected lysinoalanine from Aloc-protected Garner’s aldehyde

An expedient synthesis of orthogonally protected lysinoalanine has been developed. We have prepared a novel Garner’s aldehyde derivative bearing an Aloc group; reductive amination of this aldehyde with Fmoc-Lys-OPMB gave the lysinoalanine skeleton. This was then transformed into an orthogonally protected lysinoalanine derivative suitable for the synthesis of side-chain bridged cyclic peptides by solid phase peptide synthesis methods.     

An expedient synthesis of homophthalimides

The six-membered heterocyclic subunit of homophthalimides can be obtained by a direct, hitherto unprecedented, radical cyclisation onto an aromatic ring starting from a xanthate precursor.     

Synthesis of fused indoles by sequential palladium-catalyzed Heck reaction and N-heteroannulation

A route to 3,4-fused indoles via two consecutive palladium-catalyzed reactions; an intramolecular Heck reaction followed by a reductive N-heteroannulation is described. Using this route, a number of indoles have been prepared having a variety of ring sizes anchored to the 3- and 4-position of the indole nucleus. Furthermore, a number of functional groups, both carbon and heteroatom substituents can be introduced in (and on) the additional ring without any detrimental effects on the two reactions.     

An expedient synthesis of mellitic triimides

Heating of the solid ammonium salts obtained from treatment of mellitic acid with 3 equiv of a primary amine yields trisubstituted mellitic triimides via dehydration and imide ring closure. This surprisingly simple synthetic approach is amenable to incorporation of alkyl, aryl, and amino acid ester substituents, thereby opening broad access to a family of C(3)-symmetric organic electron acceptors.     

3-Alkylpyridines III. Total synthesis of both enantiomers of the antineoplastic marine alkaloid niphatesine D

Summary A five-step synthesis of both enantiomers of the marine alkaloid niphatesine D (3), starting from the readily available enantiomeric hydroxyalkylthiophenes5 andent-5, is described.Dedicated to Prof. Dr.E. Reimann on the occasion of his 60th birthday     

An expedient synthesis of substituted indoles

Condensation of carboxylic acid esters with organodilithium reagents derived from N-trimethylsilyl-o-toluidine or N-trimethylsilyl-o-ethyl aniline affords substituted indoles.     

An expedient asymmetric synthesis of platencin

A short and efficient synthesis of enone 3, a key intermediate in the total synthesis of platencin (2), based on an intramolecular Diels-Alder reaction is described.     

Total synthesis of makaluvamine A/D, damirone B, batzelline C, makaluvone, and isobatzelline C featuring one-pot benzyne-mediated cyclization-functionalization

Total synthesis of pyrroloquinoline alkaloids, such as makaluvamine A/D, damirone B, batzelline C, makaluvone, and isobatzelline C, was achieved featuring a one-pot benzyne-mediated cyclization-functionalization reaction. The synthetic utility was demonstrated by the construction of the common pyrrolo[4,3,2-de]quinoline skeleton.     

An expedient synthesis of an isofervenulin analogue

An efficient approach has been developed for the synthesis of an isofervenulin analogue 1 employing a one‐pot condensation‐substitution reaction of a chlorocarboethoxytriazine (electrophile) with a urea (nucleophile). The resulting cyclization reaction resulted in the synthesis of a pyrimido‐heterocycle in good yield in either acidic or basic media. The former was assisted by utilizing trimethylsilyl chloride.     

Dimerization of functional pyrroloindolizines for the synthesis of complex myrmicarin alkaloids

The union of functionalized pyrroloindolizines for the synthesis of heterodimeric products relevant to myrmicarin alkaloids is described. Design and synthesis of tricyclic substrates and new methods for their union enable the investigation of late-stage cyclopentannulation strategies. The rapid assembly of dimeric structures using unique modes of pyrroloindolizine reactivity presents a concise approach to the dimeric myrmicarins and relevant derivatives.     

An expedient synthesis of ellipticine via Suzuki-Miyaura coupling

A simple and efficient total synthesis of ellipticine was developed via the Suzuki-Miyaura coupling of sterically sensitive 2-hydroxybenzeneboronic acid with a multifunctional aryl halide using Pd(OAc)₂ as a catalyst and Cu(OAc)₂·H₂O as an additive in DMSO/H₂O as a key step followed by double N-arylation and cyclization.     

An expedient synthesis of (+)-quinolactacin A2

An expedient synthesis of quinolactacin A2 from N-methylisatoic anhydride and N-Boc-(2S,3S)-isoleucine has been achieved. The key step involves the Friedländer-type annulation of isatoic anhydride and β-ketoester derived from isoleucine.     

An expedient synthesis of diversified pyrrolizines and indolizines

A general and rapid synthesis of new families of pyrrolizines and indolizines in good overall yields via an intramolecular [3+2] cycloaddition reaction is described. Diversity of substitutions can be achieved by the appropriate choice of readily available starting materials. The experimental procedures are straightforward and are performed under neutral conditions. New syntheses are also described for the preparation of N-propargylic 2-amino-benzaldehydes and S-propargylic 2-thiobenzaldehydes.     

3-Alkenyl-5-chloropyrazoles: expedient synthesis via heterocyclization of 1,1-dichloro-4-halo-1-alken-3-ones with hydrazines

Synthesis of hard-to-reach 5-chloro-3-alkenylpyrazoles was developed via heterocyclization of alkyl-, benzyl- or dialkylhydrazines with 1,1-dichloro-4-halo-1-alken-3-ones obtained from haloacyl chlorides and vinylidene chloride. The reaction process includes the formation of intermediate 5-chloro-3-(1-haloalkyl)pyrazoles followed by dehydrohalogenation.     

A process for the rapid removal of dialkylamino-substituents from aromatic rings. Application to the expedient synthesis of (R)-tolterodine

A range of N,N-dialkylanilines have been successfully converted to the parent substituted benzenes by a novel two-step pathway. The products are obtained in good yields and optical purity of adjacent stereocenters is maintained. This technology has been applied toward the synthesis of (R)-tolterodine.     

An expedient synthesis of 2,5-disubstituted-3-oxygenated tetrahydrofurans

Single enantiomer 2,5-disubstituted-3-oxygenated tetrahydrofurans are synthesized in as little as four steps from a commercially available epoxide. The key steps are homoallylic alcohol epoxidation, palladium-catalysed alkoxy-carbonylation-lactonisation and Mitsunobu inversion. The protocol is applied to the formal total syntheses of (+)-kumausallene, (6S,7S,9R,10R)-6,9-epoxynonadec-18-ene-7,10-diol and the core of lytophilippine A.     

Palladium-catalyzed synthesis of quinoxaline derivatives

A palladium-catalyzed reductive N-heteroannulation of enamines derived from 2-nitrobenzenamines forming mixtures of 1,2-dihydroquinoxalines and 3,4-dihydroquinoxalin-2-ones is described. The reactions are performed using bis(dibenzylideneacetone)palladium(0), 1,3-bis(diphenylphosphino)propane, and 1,10-phenanthroline in DMF under 6 atm of carbon monoxide at 70 °C.     

An expedient synthesis of tetrakis(cyclopropylmethyl)methane

Synthesis of tetrakis(cyclopropylmethyl)methane, a new symmetric product has been described using the radical mediated gem-diallylation of cyclopropylmethyl xanthate as a key step and its single crystal X-ray analysis established its C2-symmetry.