Synthesis of α-(perfluoroalkyl)-ω-(trialkylsilyl)alkanols

The synthesis of alkanols of the general formula R₃Si(CH₂)_nCH(OH)R_F (n = 1–3) is elaborated and their behavior under GC-MS is studied.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1516-1519, June, 1996.     

Efficient synthesis of (S)-(−)- and (R)-(+)-enantiomers of 15-deoxyspergualin (15-DSG)

An efficient synthesis of the (S)-(−)- and (R)-(+)-enantiomers of 15-deoxyspergualin (15-DSG) is reported. The synthesis involves preparative HPLC separation and subsequent hydrogenolysis of two diastereoisomers 10a and 10b of fully protected 15-DSG penultimates. Alternatively, diastereomerically pure amide 10b (97% de) was also prepared from acid 8b (97% de), which was obtained via crystallization of a 1:1 diastereomeric mixture of 8a and 8b.     

A practical stereoselective synthesis of (S)-( - )-ofloxacin

A very efficient and practical procedure for preparation of ( S)-( - )-ofloxacin has been developed (10 steps, overall yield ≥ 45 % ) . The key step of this approach is the regioselective nucleophilic substitution of 2-position fluorine atom of 2,3,4-tirfluoronitrobenzene by (S)-glycerol acetonide.     

Synthesis of (R)-(-)-γ-amino β-hydroxy Butyric Acid (GABOB)

An efficient enantiospecific synthesis of a neuromodulator, antiepileplic and hypotensive drug (R)-(-)-γ-amino-β-hydroxybutyric acid (1) starting from (+) tartaric acid is described.     

Total synthesis of(-)-goniopypyrone

Recently,three novel styryl-lactones,goniofufurone,goniopypyrone,and 8-acetylgo-niotriol,which are cytotoxic to human tumor cells,have been isolated from the stembark of Goniothalamus species.Amongst these lactones,goniopypyrone is the mostbioactive.Its unusual natural skeleton was revealed by X-rav structure analysis to be     

Total Synthesis of (-)-α-Pinguisene

In previous work from our laboratory, we demonstrated that α-carbonyl radical cyclization reactions can serve efficiently as key steps in total synthesis of natural products.1 In this presentation,we report the total synthesis of (-)-α-pinguisene from enone 1 via α-carbonyl radical cyclization.     

Deracemization of 5-(4-hydroxyphenyl)-5-phenylhydantoin (HPPH): practical synthesis of (−)-(S)-HPPH

In the presence of 10% NaOH in boiling MeOH enantiomerically enriched HPPH is racemized. This permits the deracemization of HPPH in the presence of brucine, giving enantiomerically pure (−)-(S)-HPPH [(−)-(S)-5-(4-hydroxyphenyl)-5-phenylhydandoin].     

Efficient synthesis of (−)-(R)- and (+)-(S)-rolipram

A novel, efficient and protecting group free enantioselective synthetic approach of (?)-(R)-1 and (+)-(S)-rolipram 2 is described employing the organocatalyzed asymmetric Michael addition, Henry condensation, Wittig olefination and reductive lactamization reactions as key steps.     

Total Synthesis of (-)-Kaerophyllin,(-)-Hinokinin and (±)-Isohinokinin

Kaerophyllin (1) ,hinokinin (2 )andtheiranalogue isohinokinin (3)belongtothedibenzylbutyrolactone lig nans .Kaerophyllin (1)wasisolatedfromtherootofspot tedcowparsley (ChaerophyllummaculatumWilld .) 1andhinokinin (2 )wasisolatedfromtheheartwoodofLiboce drusformosanaFlorin .2 AccordingtoMacRaeandTow ers ,3afivememberedlactoneringandamethylenedioxylgroupwereimportantstructuralcharacteristicswhichcon tributetotheactivityoflignansasantitumoragents .More over ,anunsaturateddoublebondbetweenC3—…     

A concise total synthesis of (±)- and (-)-okilactomycin D

The spirotetronate okilactomycin D (7) has been efficiently synthesized by a route featuring a substrate-controlled, diastereoselective (8:1) intramolecular Diels-Alder (IMDA) reaction of 11. The assigned absolute configuration of (-)-7 was confirmed.     

Total Synthesis of (-)-Baimuxifuranic Acid

ThenatieChenmanginclha,oneofthemoStbeandexpensivCherbaldrugSin~tionalChjnsemdednesisthewoodypartofAquIIarasinensisW.)Gilg.,whoseVofatileoilseforitaIUUnberofinterestinbiologicalandphannacologicalactivities,suchasanestheha,muscularrelaxationandanalgesta'.ReCentiyYanetaI2isolated(-)taim~cacid(1)frOmtheVOboleoilofChenAlang,anddeennineditSStIUCtUrbySpeCtrscoPicmethodandred~1toaknowncornPOunisobaimndnolCoInPOun1isthefirStcarboxylicacidwithdihydragarohanskeletonisolatedfromnisources.He…     

Synthesis of (±)-7-hydroxylycopodine

A six step synthesis of (±)-7-hydroxylycopodine has been achieved in 5% overall yield. In the key step, a Prins cyclization of a bicyclic keto alkyne in 60% H(2)SO(4) forms a tricyclic dihydroxy amino ketone.     

Synthesis of (S)-(−)-β-cuparenone and (S)-(−)-cuparene

A short and efficient synthesis of the title compounds is described. (S)-(−)-β-Cuparenone was prepared in 31% yield from p-tolualdehyde and mesityl oxide in eight steps. Absolute stereochemistry was established by means of a diastereoselective cyclopropanation using (R,R)-hydrobenzoin as a recoverable auxiliary.     

Synthesis of (±)-7-hydroxylycopodine

A seven-step synthesis of (±)-7-hydroxylycopodine that proceeds in 5% overall yield has been achieved. The key step is a Prins reaction in 60% sulfuric acid that gave the key tricyclic intermediate with complete control of the ring fusion stereochemistry. A one-pot procedure orthogonally protected the primary alcohol as an acetate and the tertiary alcohol as a methylthiomethyl ether. The resulting product was converted to 7-hydroxydehydrolycopodine by heating with KO-t-Bu and benzophenone in benzene followed by acidic workup. During unsuccessful attempts to make optically pure starting material, we observed the selective Pt-catalyzed hydrogenation of the 5-phenyl group of a 4,5-diphenyloxazolidine under acidic conditions and the Pt-catalyzed isomerization of the oxazolidine to an amide under neutral conditions. In attempts to hydroxylate the starting material so that we could adapt this synthesis to the preparation of (±)-7,8-dihydroxylycopodine (sauroine) we observed the novel oxidation of a bicyclic vinylogous amide to a keto pyridine with Mn(OAc)(3) and to an amino phenol with KHMDS and oxygen.     

Supramolecular inclusion complexes of β-cyclodextrin with 4-(acyloxy)-4-(cyclopropylethynyl)-1-(2-ethoxyethyl)piperidines

4-Acyloxy-4-(cyclopropylethynyl)-1-(2-ethoxyethyl)piperidines have been synthesized by reaction of 1-(2-ethoxyethyl)piperidin-4-one with cyclopropylacetylene and subsequent acylation of intermediate 4-(cyclopropylethynyl)piperidin-4-ol. The resulting esters react with β-cyclodextrin to give supramolecular inclusion complexes. The complexation is accompanied by inclusion of the N-ethoxyethyl fragment of one substrate molecule in the inner cavity of one receptor molecule. The structure of 4-acyloxy-4-(cyclopropylethynyl-1-(2-ethoxyethyl)piperidines and their inclusion complexes with cyclodextrin has been studied by NMR spectroscopy.     

Straightforward Syntheses of the Three Possible Isomers of (±)-2-[3-(Hydroxybenzoyl) phenyl]propanoic Acid,Metabolites of (±)-Ketoprofen

The o-, m- and p- isomers of (±)-2-[3-(hydroxybenzoyl)phenyl] propanoic acid (11, 12 and 4) have been prepared from 3-bromopropiophenone or m-propionylbenzoic acid, via 7, 8 and 2, which were submitted to Tl(III) nitrateinduced rearrangement, followed by hydrolysis of the ester and ether functions.     

Electrochemical synthesis of π-indenyl-π-(3)-1,2-dicarbollyliron(III)

Co-electrolysis of potassium 1,2-dicarbadodecahydroundecaborate and indene in 0.1N sodium bromide solution in dimethylsulfoxide using iron electrodes afforded -indenyl--(3)-1,2-dicarbollyliron(III).Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 764–765, April, 1993.     

Silicon-induced diastereoselectivity of the catalyzed phosphorylation of 1-(perfluoroalkyl)-ω (trialkylsilyl)alkan-1-ols

The stereochemistry of catalytic phosphorylation of 1-(perfluoroalkyl)--(trialkylsilyl)alkan-1-ols with pentavalent phosphorus acid monochlorides (phosphonochloridates, methyl(phenyl)phosphinic chloride, and phosphorochloridates) was studied. The effects of the structures of alcohols and phosphorylating agents on the degree of the reaction diastereoselectivity were investigated. Methylphosphonochloridates were found to react most stereoselectively; the diastereoselectivity of the phosphorylation is independent of the donor or acceptor character of substituents at the phosphorus atom, being determined by their volumes. In the series of silylalkanols, the diastereoselectivity of the reaction the higher the closer the Si atom to the reactive site of the molecule, the larger the volume of the perfluoroalkyl substituent, and the more pronounced the electron-withdrawing properties of the substituents at the Si atom. A reaction mechanism is proposed that rationalizes the stereoselectivity of the reaction.Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1930–1936, September, 2004.     

Synthetic studies towards(-)-deserpidine:Total synthesis of the stereoisomer and derivative of (-)-deserpidine

The asymmetric synthesis of 16,17,20-epi-deserpidine and a derivative of(-)-deserpidine has been achieved.Key feature s in the assembly of the pentacyclic framework include a visible-light photocatalytic intra-/inter-/intramolecular radical cascade reaction to construct the tetracyclic ABCD ring system in one-pot and an intramolecularaldol reaction to forge the cyclohexane E ring.