Solid-phase synthesis of indolizidine and quinolizidine derivatives

An efficient method for the construction of simple indolizidine and quinolizidine derivatives on solid support has been developed. An intramolecular tandem Michael reaction initiated by the nucleophilic attack of a suitably placed amino group on the tethered Wittig condensation products between 4- or 5-aminoaldehydes attached to a trityl chloride resin and 4-[(4-methylphenyl)sulfonyl]-1-(triphenylphosphoranylidene)-2-b utanon e is the key step.     

Synthetic studies on erythromycin derivatives: reactivity of the C12-21 alkene

The reactivity of the C12-21 alkene of some erythromycin A derivatives was studied. This double bond was easily oxidized to the corresponding epoxide with excellent stereoselectivity. A single crystal X-ray structure showed that the epoxide moiety was on the same side as the acetonide. When an erythromycin derivative containing a C12-21 alkene was treated with diazomethane a [3+2] cycloaddition affording a pyrazoline occurred. In the case of 6-O-allylated erythromycin derivatives the C12-21 alkene was selectively epoxidized in the presence of the 6-O-allyl moiety. These results show that the C12-21 alkene is an active reaction site, which can be used for useful further modification of erythromycin derivatives.     

Synthetic and structural studies of donor-functionalized alkoxy derivatives of gallium

The synthesis of a range of alkyl/chloro-gallium alkoxide and amido/alkoxide compounds was achieved via a series of protonolysis and alcoholysis steps. The initial reaction involved the synthesis of [Me(Cl)Ga{N(SiMe(3))(2)}](2) (1) via methyl group transfer from the reaction of GaCl(3) with two equivalents of LiN(SiMe(3))(2). Reaction of 1 with varying amounts of ROH resulted in the formation of [Me(Cl)Ga(OR)](2) (2, R = CH(2)CH(2)OMe; 3, CH(CH(3))CH(2)NMe(2)), [Me(Cl)Ga{N(SiMe(3))(2)}(μ(2)-OR)Ga(Cl)Me] (4, R = CH(2)CH(2)NMe(2)), or [MeGa(OR)(2)] (5, R = CH(CH(3))CH(2)NMe(2)). Compound 4 represents an intermediate in the formation of dimeric complexes, of the type [Me(Cl)Ga(OR)](2), when formed from compound [Me(Cl)Ga{N(SiMe(3))(2)}](2). A methylgallium amido/alkoxide complex [MeGa{N(SiMe(3))(2)}(OCH(2)CH(2)OMe)](2) (6) was isolated when 2 was further reacted with LiN(SiMe(3))(2). In addition, reaction of 2 with HO(t)Bu resulted in a simple alcohol/alkoxide exchange and formation of [Me(Cl)Ga(O(t)Bu)](2) (7). In contrast to the formation of 1, the in situ reaction of GaCl(3) with one equivalent of LiN(SiMe(3))(2) yielded [Cl(2)Ga{N(SiMe(3))(2)}](2) in low yield, where no methyl group transfer has occurred. Reaction of alcohol with [Cl(2)Ga{N(SiMe(3))(2)}](2) was then found to yield [Cl(2)Ga(OR)](2) (8, R = CH(2)CH(2)NMe(2)), and further reaction of 8 with LiN(SiMe(3))(2) yielded the gallium amido alkoxide complex, [ClGa{N(SiMe(3))(2)}(OR)](2) (9, R = CH(2)CH(2)NMe(2)), similar to 6. The structures of compounds 4, 5, 7, and 8 have been determined by single-crystal X-ray diffraction.     

A mass-spectrometric study of derivatives of the quinolizidine group

Summary The results of a mass-spectrometric study of 1- and 1,3-substituted derivatives of cis- and transquinolizidines are given. The compound investigated formed, in addition to the common ions with m/e 124, 110, 97, 54, and 41, ions specific for the trans- and cis-linkage of the rings and ions characteristic of the side chains occupying equatorial or axial positions. In addition, the mass spectra of the cis-quinolizidine derivatives are characterized by a small number of strong peaks and by a low intensity of the molecular ions.V. I. Lenin Tashkent State University. Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 194–199, March–April, 1972.     

Synthetic and structural studies on 1,2,4-dithiazolidine-3,5-dione derivatives

Methods have been developed for the N-alkylation of 1,2,4-dithiazolidine-3,5-dione 2 and the subsequent conversion of the N-alkylated derivatives into isocyanates 5. An extension of this methodology onto a solid-support is also reported. X-ray crystallographic analysis has been carried out on potassium 1,2,4-dithiazolidine-3,5-dione 3 for structural comparison with the parent heterocycle 2.     

Stanna-Brook rearrangement of carboxylic acid derivatives. Synthetic utility and mechanistic studies

[reaction: see text] The reaction of R(3)SnLi with carboxylic acid derivatives proceeds through a novel, very fast stanna-Brook rearrangement that generates alpha-alkoxyorganolithium compounds as intermediates. The outcome of these reactions depends on the nature of the carboxyl derivatives. Reaction of R(3)SnLi with ester derivatives gives rise to coupled products through a novel C-C bond formation reaction. Experimental evidence of the detailed reaction mechanism is provided.     

Enantioselective synthesis of indolizidine and quinolizidine derivatives from chiral non-racemic bicyclic lactams

Chiral non-racemic bicyclic lactams 2b,c, derived from (R)- and (S)-phenylglycinol, were used in the enantioselective synthesis of (−)-lupinine and 5-epitashiromine, respectively. The efficiency of the synthesis relied on the high diastereoselectivities of formation and reduction of compounds 2b,c.     

Synthetic studies of organodi-π-cyclopentadienyl- titanium (III) derivatives

Two synthetic routes to compounds of the type π-Cp₂Ti^IIIR (R=CH₃, CH₂Si(CH₃)₃, C₆F₅) have been investigated: (a) chemical reduction of π-Cp₂Ti^IV(R)Cl by zinc or aluminum metal in tetrahydrofuran, and (b) conventional organometallic syntheses using organo-lithium or -magnesium reagents and [π-Cp₂Ti^IIICl]₂. The preferred route is via an organolithium reagent, since chemical reduction gives a mixture of products. Green, monomeric complexes (R = CH₂Si(CH₃)₃, C₆F₅) were isolated and characterised. From the reaction of π-Cp₂Ti^IVCl₂ and trimethylsilylmethyllithium in a 1/1 ratio, π-CpTi^IV [CH₂Si(CH₃)₃]₃ was obtained. Unlike π-Cp₂Ti^IIIC₆F₅, π-Cp₂Ti^IIICH₂Si(CH₃)₃ does not form a blue complex with molecular nitrogen.     

Synthetic studies toward SNF4435 C and SNF4435 D

[reaction: see text] A synthetic approach toward the immunosuppressants SNF3345 C and SNF4435 D featuring a tandem Stille coupling/electrocyclization cascade is described.     

Synthetic studies towards lagunamide C: Polyketide assembly investigations

Lagunamide C is a depsipeptide natural product with low nM cytotoxicity towards numerous cancer cell lines. Synthetically, it is disconnected to a pentapeptide backbone and polyketide unit that possesses four stereogenic centers, of which two of centers are in question (C38 & 40). Our model system highlights a high-selective aldol addition via a Crimmin’s auxiliary setting the C40 ester linkage, and a non-facially selective cyclopropanation with subsequent ring opening for the installation of the C38 methyl center.     

Natural abundance 13C NMR studies of perezone and derivatives

Assignment of all ¹³C chemical shifts of perezone (1) and some derivatives was possible using time averaged 25·15 MHz spectra with the aid of proton noise modulated and CW decoupling. Rapid interconversion of tautomeric forms of 2,5-dihydroxy-1,4-benzoquinones is deduced from the ¹³C spectra.     

Comparative mass-spectrometric investigation of quinolizidine alkaloids and cytisine,sparteine, and matridine derivatives

The low- and high-resolution mass spectra of pachycarpine, tetrahydrodesoxocytisine, matridine, α-isolupanine, tetrahydrocytisine, matrine, d-thermopsine, cytisine, and isosophoramine, as well as some of their stereoisomers and deutero analogs, make it possible with a high degree of probability to relate the investigated compounds to one or another group of quinolizidine alkaloids.     

Enantiodivergent synthesis of the quinolizidine poison frog alkaloid 195C

Herein, we describe the enantiodivergent synthesis of the 1,4-cis-disubstituted quinolizidine alkaloid 195C. Although the stereoselectivity of the final hydrogenation reaction was low, we have proposed the first chiral total synthesis of both (−)- and (+)-195C as an enantiodivergent process.     

Synthetic studies of the formation of oxazoles and isoxazoles from N-acetoacetyl derivatives: scope and limitations

[reaction: see text] The preparation of two types of heterocycles, oxazoles and isoxazoles, were achieved in good yields in a rapid and simple way by using N-acetoacetyl derivatives. Steric and electronic effects caused by the nature of the substituents at C1, C2, and C3 were studied. The best results were obtained with a chiral oxazolidinone moiety on C1 derived from (1R,2S)-(-)-norephedrine.     

Theoretical studies of C60/C70 fullerene derivatives: C60O and C70O

A semiempirical (AM1) calculation on the structures and stabilities of isomers of the fullerene derivatives C₆₀O and C₇₀O is carried out. The ozonolysis reaction mechanism and the thermodynamics of the compounds are studied. The two isomers of C₆₀O (56 bond and 66 bond) formed by an oxygen atom bridging across a C-C bond have an epoxide-like or an annulene-like structure. According to the ozonolysis reaction mechanism and kinetic factor analysis, the possible products of this ozonolysis reaction are C₆₀O with oxygen bridging over the 66 bond (C_2v) as an epoxide-like isomer and that with oxygen bridging over the 56 bond (C_s) as an annulene-like isomer. Further, the sixteen isomers of C₇₀O (both epoxide-like and annulene-like structures) have been studied with respect to the same reaction mechanism. The most possible product in this ozonolysis reaction contains oxygen bridging across in the upper part (66 bond in C₇₀O-2 or C₇₀O-4) as an epoxide-like structure. The other possible product is C₇₀O-8 (annulene-like structure), in which oxygen bridges across an broken equatorial CC bond in C₇₀ (D_5h). The vibrational frequency analysis and the electronic structure of the selected C₆₀O and C₇₀O isomers are generated for experimental characterisation. The experimental results indicate that C₆₀O and C₇₀O may decompose into the odd number fullerenes C₅₉ and C₆₉. We therefore studied the structures of C₅₉ and C₆₉ also.     

Indolizidine and quinolizidine alkaloids

This review covers the isolation, structure determination, synthesis, chemical transformations and biological activity of indolizidine and quinolizidine alkaloids from microbial, plant and animal sources. Included in the review are the hydroxylated indolizidines lentiginosine, swainsonine, castanospermine and their analogues; alkaloids from animal sources, including ants, amphibians and beetles; ipalbidine, phenanthroindolizidines and related alkaloids; Lycopodium alkaloids; lupine alkaloids; and alkaloids from bacterial and marine sources. The literature from July 2002 to June 2003 is reviewed, and 174 references are cited.     

Indolizidine and quinolizidine alkaloids

This review covers the isolation, structure determination, synthesis, chemical transformations and biological activity of indolizidine and quinolizidine alkaloids. Included in the review are the hydroxylated indolizidines lentiginosine, swainsonine, castanospermine and their analogues; alkaloids from animal sources, including ants, amphibians and beetles; indolizidine alkaloids from the genera Polygonatum, Prosopis and Elaeocarpus; indolizidine and phenanthroindolizidine alkaloids; alkylquinolizidine alkaloids, including myrtine, epimyrtine, plumerinine and Lycopodium metabolites; Lythraceae and Nuphar alkaloids; lupine alkaloids; and alkaloids from marine sources. 150 references are cited.