bluuebunny/crossref_metadata_2025_split huggingface dataset:
Hydroacridine, XIII. Sterischer Verlauf der N‐Oxidation von N‐Alkyl‐Derivaten des (4aα,8aβ,9aβ,10aα)‐Tetradecahydroacridins (α‐Perhydroacridin)
Authors: Potmischil Francisc , Naiman Marian 
Published: July 2007

Hydroacridines, XIII. — Steric Course of the N‐Oxidation of N‐Alkyl Derivatives of ((4aα,8aβ,9aβ,10aα)‐Tetradecahydroacridine (α‐Perhydroacridine)Diese Arbeit wurde auf der 5. rumänischen Konferenz für allgemeine und angewandte physikalische Chemie, Bukarest, 1. −4. September 1976, mitgeteilt.
The oxidation of N‐methyl‐α‐perhydroacridine (1), with hydrogen peroxide at room temperature occurs approximately with 83% by equatorial, and approximately with 17% by axial attack of the oxygen on the nitrogen atom. The oxidations of N‐ethyl‐ (2) and N‐benzyl‐α‐perhydroacridine (3) yield only the N‐oxides with axial oxygen (2′a and 3′a, respectively).
En route to thromboxane compounds from carbohydrates, I. Synthesis of the unsaturated sugar precursors
Authors: Pelyvás István , Lindhorst Thisbe , Thiem Joachim 
Published: July 2007

AbstractAllyl 4‐C‐[(carboxamido)‐ and (ethoxycarbonyl)methyl]hex‐2‐enopyranosides 18a–c, representing chiral precursors for the carbohydrate‐based construction of the ring systems of thromboxane A2 and B2 were prepared by means of the Claisen‐type rearrangement of the suitably substituted hex‐3‐enopyranosides 7a, b. The latter sugars were synthesized from allyl α‐D‐glucopyraoside (9) by modification of known procedures, including selective O‐benzoylation with 1‐(benzoyloxy)‐1H‐benzotriazole (11), and Tipson‐Cohen sulfonyl ester elimination of the 3,4‐di‐O‐mesylates 16 and 17. Studies on the corresponding methyl glycosides 8a–c showed a reduced stability of the 6‐O‐(tert‐butyldiphenylsilyl) ether group under the Tipson‐Cohen reaction conditions.
Stereoselektive Synthese des substituierten Morphan‐Gerüstes ausgehend von 4‐Acetamidocyclohexanon
Authors: Teuber Hans‐Joachim , Tsaklakidis Christos , Bats Jan Willem 
Published: July 2007

Stereoselective Synthesis of the Substituted Morphane Framework Starting with 4‐Acetamidocyclohexanone4‐Acetamidocyclohexanone (2), prepared from 4‐acetamido‐cyclohexanol (1), has been transformed into the ethyleneacetal 3b which was amidated with pyruvic and 2‐oxobutyric acid to give 3c and d, respectively. After removal of the protecting group (4a, b) the amide is treated with sodium hydride in tetrahydrofuran or with sodium ethylate in ethanol. Depending on the reaction conditions 4b is transformed into the aldol 6 or the cyclised aldol 5b (5a from 4a, respectively) with 2‐azabicyclo[3.3.1]nonane structure and endo‐positioned hydroxy group. Constitution and stereochemistry has been proved by X‐ray structure analysis of 7a. The stereochemistry of the ring closure reaction corresponds to the transition state postulated.
Tetra‐O‐acetyl‐β‐D‐glucopyranosyl chloride: Occurrence of gg and gt rotamers in the crystal and correlation between conformation at C‐6 and anomeric stabilization
Authors: Lichtenthaler Frieder W. , Rönninger Stephan , Kreis Uwe 
Published: July 2007

AbstractAn X‐ray structural analysis of 2,3,4,6‐tetra‐O‐acetyl‐β‐D‐glucopyranosyl chloride (5β) shows the crystal lattice to contain consecutive layers of two forms, each in the 4C1 conformation, but differing in the orientation of the 6‐acetoxy group relative to the pyranoid ring: the gauche‐gauche (gg) rotamer, exhibiting standard bond lengths and torsional angles, and the gauche‐trans (gt) form, in which an unusually long C‐5—O‐5 bond distance of 1.536 Å is observed, though without major distortion of the chair conformation. In solution, only the gg form prevails. The similarity of conformational features of 5β in its gg form and of its β‐methoxy analog 7β is so close that the anomeric effects for equatorial Cl and OCH3 on a pyranoid ring must be grossly identical. — Force‐field calculations on the anomeric 1‐chloro‐ and 1‐methoxy derivatives of tetra‐acetyl‐D‐glucopyranose allow a realistic estimation of the magnitude of the anomeric effect and a surprisingly accurate assessment of the degree of anomeric stabilization in the individual C‐6 rotameric forms, the gg conformer invariably being the energetically most favored.
Chemoenzymatische „Chiral‐Pool”︁‐Synthese von (+)‐exo‐Brevicomin aus Kohlenhydraten mit Fructose‐1,6‐diphosphat‐Aldolase
Authors: Schultz Michael , Waldmann Herbert , Kunz Horst , Vogt Walter 
Published: July 2007

Chemoenzymatic “Chiral‐Pool” Synthesis of (+)‐exo‐Brevicomin from Carbohydrates Using Fructose 1,6‐Diphosphate AldolaseFructose‐1,6‐diphosphate aldolase (EC 4.1.2.13) catalyzes the stereospecific aldol reaction between 1,3‐dihydroxyacetone phosphate (4) and 5‐oxohexanal (3) or its 5‐dithiane‐protected analog 8. The products of the aldol reactions are dephosphorylated with acid phosphatase (EC 3.1.3.2). Whereas the aldol adduct of 3 cyclizes spontaneously to give the bicyclic brevicomin precursor 3, the adduct of 8 first has to be deprotected with sulfuryl chloride and wet silica gel. The resulting bicyclic α‐hydroxy ketone 3 is reduced with LiAlH4 to form the 1,2‐diol 14 which is then deoxygenated to give the vinyl compound 17 by treatment of the corresponding dixanthate 15 with tributyltin hydride or by treatment of the corresponding mesylate 16 with sodium naphthalenide. The olefin 17 is finally converted to (+)‐exo‐brevicomin (1) by hydrogenation with diimide.
Structure — Odor correlation, X. Synthesis and olfactive properties of 7‐oxanorbornanes
Authors: Weyerstahl Peter , Brendel Joachim 
Published: July 2007

AbstractThe 7‐oxanorbornanes 17–19 are prepared by Diels‐Alder reaction of 2,5‐dimethylfuran (1) and 2‐isopropyl‐5‐methylfuran (2) with 2‐chloro‐ (3) or 2‐acetoxyacrylonitrile (4). The adducts 5–10a,b are hydrogenated (→ 11–16a, b) and subsequently hydrolyzed. From 1 and acrylonitrile (21) the stereoisomers 25a, b can be obtained via 23a, b in various ratios, depending on the reaction conditions. The Grignard reaction of the exo nitrile 25a with MeMgI or iPrMgI gives the exo ketones 27a and 28a. In the case of the endo nitrile 25b the same reaction favors the formation of side products. LiAlH4 reduction of 17, 26b, 27b, and 28a yields the 7‐oxanorbornanyl alcohols 29b–31b and 32a. — The fragrance of the ketones 18 and 19 is very similar to that of the substructures 1,4‐cineol and menthone. The smell of ketones 27 and 28 as well as of the alcohols 29b–31b is weak. Odor quality and strength of the alcohols 32a′, a″ are determined by their ability to form more or less easily an intramolecular hydrogen bond leading to a rigid conformation which is responsible for the typical minty‐camphoraceous odor.
Darstellung 2‐methoxysubstituierter Pyrrole durch intramolekulare Aza‐Wittig‐Reaktionen
Authors: Montforts Franz‐Peter , Schwartz Ulrich Manfred , Maib Piotr , Mai Gerhard 
Published: July 2007

Preparation of 2‐Methoxy‐Substituted Pyrroles by Aza‐Wittig Reactionsα‐Halo ketones and dimethyl malonate can be transformed by Knoevenagel condensation and nucleophilic displacement of halogen with sodium azide into the azide esters 10. These azides undergo ring closure to 2‐methoxy‐substituted pyrroles 11 by intramolecular Aza‐Wittig reaction.
Biologically active glycosides from asteroidea, XXIV. Stereochemistry of the four diastereomers of phytosphingosine
Authors: Sugiyama Shigeo , Honda Masanori , Komori Tetsuya 
Published: July 2007

AbstractDiastereomeric D‐ribo‐(2S,3S,4R)‐, D‐lyxo‐(2S,3S,4S)‐, D‐arabino‐(2S,3R,4S)‐, and D‐xylo‐(2S,3R,4R)‐C16‐phytosphingosine tetraacetates 2–5 were synthesized from the oxazoline 11 derived from (S)‐serine. Detailed physical data were obtained and the stereochemistry can be readily identified, regardless of any new phytosphingosine moiety of the glucosphingolipids which may be detected in nature.
Preparation of some fully chloroacetylated glycopyranosyl bromides: Useful intermediates for the synthesis of base‐ and hydrogenolysis‐sensitive glycosides
Authors: Ziegler Thomas 
Published: July 2007

AbstractChloroacetylation of alkyl glycopyranosides of β‐D‐galactose, β‐D‐glucose and α‐D‐mannose as well as of free D‐glucose, D‐galactose, D‐mannose and D‐xylose, using chloroacetic anhydride as acylating reagent, gave the corresponding fully chloroacetylated pyranose derivatives in excellent yields. From D‐glucose, 1,2,3,6‐tetra‐O‐chloroacetyl‐α‐D‐glucopyranose (9) was also obtained. Subsequent treatment of the fully chloroacetylated α‐D‐glycopyranoses 3, 8, 13 and 15 of galactose, glucose, mannose, and xylose, respectively, with HBr resulted in 2,3,4,6‐tetra‐O‐chloroacetyl‐α‐D‐galactopyranosyl bromide (4, 98%), ‐glucopyranosyl bromide (10, 92%), ‐mannopyranosyl bromide (14, 72%) and 2,3,4‐tri‐O‐chloroacetyl‐α‐D‐xylopyranosyl bromide (16, 68%). 10 reacted with D‐pantholactone (17) and silver trifluoromethanesulfonate under acidic conditions to give the corresponding α‐linked (18, 45%) and β‐linked (20, 38%) glucopyranosides. Under basic conditions the corresponding ortho ester product 21 was formed (92%) which upon treatment with BF3 gave the glucosides 18 and 20. Silver silicate as the catalyst gave only traces of 18. Thus, 20 was isolated in 80% yield. Reaction of 10 with silver crotonate and silver laurate gave 1‐O‐crotonoyl‐ (22) and 1‐O‐lauroyl‐2,3,4,6‐tetra‐O‐chloroacetyl‐β‐D‐glucopyranose (24), respectively. 18 and 22 were dechloroacetylated with thiourea, affording the corresponding deblocked glucose derivatives 19 and 23, respectively.
One‐pot synthesis of polyfunctionally substituted 2,3‐dihydrothiazoles and thiazolidinones
Authors: Mohareb Rafat M. , Sherif Sherif M. , Abdel‐Aal Fatma A. M. , Sayed Nadia I. A. 
Published: July 2007

AbstractThe reaction of phenyl isothiocyanate with the active methylene reagents 1a–e gives the nonisolable 1:1 adducts 2a–e. The latter react with α‐halogenated compounds, e.g. phenacyl bromide, bromoacetyl bromide, chloroacetone, chloroacetonitrile and some hydrazonoyl halides to give the corresponding polyfunctionally substituted 2,3‐dihydrothiazoles or thiazolidinone ring systems.
Neue 21,22‐Dioxaporphyrin‐5(23H)‐one, Sauerstoff‐Analoga der Oxophlorine
Authors: Rusch Roland , Gast Achim , Breitmaier Eberhard 
Published: July 2007

New 21,22‐Dioxaporphyrin‐5(23H)‐ones, Oxygen Analogues of Oxophlorins12,13,17,18‐Tetraalkyl‐21,22‐dioxaporphyrin‐5(23H)‐ones 10 (21,22‐dioxa‐5‐oxophlorins) have been synthesized by MacDonald cyclization from Bis(5‐formyl‐2‐furyl)methanone (4) and 3,3′,4,4′‐tetraalkyl‐2,2′‐dipyrrylmethanes 8 in dichloromethane with acetic anhydride. IR, UV and NMR spectroscopic data have been compared with those of 3,7,13,17‐tetraethyl‐2,8,12,18‐tetramethyl‐21H,23H‐porphyrin‐5(22H)‐one (12) which has also been newly synthesized. NMR shifts did not provide evidence for the diaza[18]annulene tautomers 11 of the 21,22‐dioxaphlorin‐5‐ones 10.
Studies on alkyl‐substituted, heteroaromatic carbonitriles: Novel synthesis of thienoazines and benzoazines
Authors: Elnagdi Mohamed Hilmy , Erian Ayman Wahba 
Published: July 2007

AbstractThe alkyl‐substituted heterocyclic carbonitriles 1–3 react with elemental sulphur to yield the thienoazines 7, 11 and 13, respectively. Whereas 7 reacts with acrylonitrile to afford a [4+2] cycloaddition product with elimination of hydrogen sulphide, compounds 11 and 13 are not converted into cycloadducts. The quinoline 9a and the quinazoline 14 are obtained by reaction of 1 and 3, respectively, with formaldehyde and malononitrile. The thienopyridines 16 are produced by reaction of 6a, c with benzylidinemalonitrile. Furo[3,4‐f]indazole 19 is prepared by [4 + 2] cycloaddition of the thienopyrazole 18 with maleic anhydride. The effect of the substituent of the thienyl moiety of the thienopyridazine ring system on its reactivity toward electron‐poor olefins has been investigated.
P(III)‐Acridinderivate als Synthesebausteine für die Festphasensynthese nichtradioaktiv markierter Oligonucleotide
Authors: Möller Uwe , Cech Dieter , Schubert Frank 
Published: July 2007

P(III)‐Acridine Derivatives as Building Blocks for the Solid‐Phase Synthesis of Non‐Radioactively Labelled OligonucleotidesIn contrast to 9‐(2‐hydroxyethyl)‐10‐methylacridinium salts 5 9‐(2‐hydroxyethyl)acridine (2) proved to be a useful intermediate for the synthesis of 2‐(9‐acridinyl)ethyl phosphoramidites 8 or 2‐(9‐acridinyl)ethyl H‐phosphonates 9 suitable for the introduction of acridine into oligonucleotides. The phosphorous compounds 8 and 9 were synthesized by modified standard procedures. The phosphoramidites and H‐phosphonates of 2 are attached to the 5′ end of different oligonucleotides in the last cycle of the solid‐phase synthesis.
The synthesis of 3‐deoxy‐L‐fucose (3,6‐dideoxy‐L‐xylo‐hexose)
Authors: Lindhorst Thisbe K. , Thiem Joachim 
Published: July 2007

AbstractThe synthesis of 3‐deoxy‐L‐fucose (19) could not be achieved by an inversion procedure, starting from the 3‐O‐triflate‐activated derivatives 8 or 9, respectively. Also the Mitsunobu reaction with the 3‐OH‐unblocked sugars 6 or 7 did not lead to the desired compounds. Instead, the formation of the unexpected side products 10, 11 and 12 was observed and interpreted. However, an equilibrium mixture of 3‐deoxy‐L‐fucose 19 and 21 was successfully synthesized by utilizing a Barton‐type deoxygenation of methyl 2,4‐di‐O‐benzoyl‐α‐L‐fucoside (7). The latter compound could be obtained from methyl α‐L‐fucoside (1) in a one‐pot reaction and crystallization in approximately 70% yield.
Novel, diastereoselective synthesis of 3‐amino‐1‐alkanols
Authors: Oszbach György , Neszmélyi András 
Published: July 2007

AbstractBenzaldehyde adds to 1‐pyrrolidinylcyclohexene under mild conditions giving the amino ketone 3a. The unstable ketone was reduced to the epimeric alcohols 4 and 5, the stereochemistry of which was determined by 2D‐NMR correlation spectroscopy.
Synthesis and biological activities of new analogues of thymopoietin II (32–36)
Authors: Nawrocka‐Bolewska Eleonora , Siemion Ignacy Z. , Mihelić Mirna , Voelter Wolfgang 
Published: July 2007

AbstractThe pentapeptide fragment of thymopoietin II (32–36) (TP5) shows similar biological activities as the parent molecule, also induces E‐rosette formation, and enhances phagocytosis. In order to elucidate further structural and functional requirements for its activity we decided to replace each amino acid residue of the pentapeptide by proline moieties.
Inter‐ and intramolecular hetero Diels‐Alder reactions, 28. Synthesis of (±)‐secologanin aglucone O‐ethyl ether and derivatives by tandem Knoevenagel hetero Diels‐Alder reaction
Authors: Tietze Lutz F. , Meier Heinrich , Nutt Heinrich 
Published: July 2007

AbstractThe tandem Knoevenagel hetero Diels‐Alder reaction of 4,4,4‐trichloro‐3‐oxobutanal (4), the malondialdehyde derivative 11a, and the enol ether 13 was followed by separation of the diastereomers and treatment with DBU in methanol. Thermolysis in xylene then gave the secologanin derivative 25a in 14% yield with the correct relative stereochemistry at all stereogenic centers. Hydrolysis of the dithiane moiety afforded secologanin aglucone O‐ethyl ether 9 in 86% yield. In a similar way, 25b and 25c were obtained in 14% and 28% yield from the malondialdehyde derivatives 11b and 11c, respectively. Reduction of 9 with sodium borohydride gave swerosid aglucone O‐ethyl ether 24 in 69% yield. The dihydrosecologanin derivative 32 was obtained in 20% yield by reaction of 5, 11c, and 26 followed by methanolysis. In this transformation the initially formed cycloadducts 27 and 28 were isolated; 33, the other type of product obtained by reaction of the second heterodiene moiety in the intermediate Knoevenagel product 18, was also found.
New acetylenes from Chrysanthemum coronarium L.
Authors: Sanz Juan Francisco , Falcó Enrique , Marco Juan Alberto 
Published: July 2007

AbstractThe investigation of the aerial parts of Chrysanthemum coronarium yielded, in addition to several known compounds, two new acetylenic sulfoxides 9 and 10, and a new thiophene spiroacetal enol ether 11. Their structures were deduced by spectroscopic and chemical methods.
Synthesis of (+)‐disparlure using the reaction of 6‐methylheptyl phenyl sulfone with trimethylsilyloxirane and asymmetric epoxidation
Authors: Marczak Stanislaw , Masnyk Marek , Wicha Jerzy 
Published: July 2007

AbstractReaction of lithiated sulfone 3 with trimethyl(oxiranyl)silane 4, followed by acid hydrolysis, afforded the (Z)‐allylic alcohol 6 contaminated with its (E) isomer. Epoxidation of 6 by the Sharpless procedure yielded the hydroxy epoxide, which was isolated as its enantiomerically pure 3,5‐dinitrobenzoyl derivative 7 and transformed into (+)‐disparlure 1 via alcohol 8 and tosylate 9.
N‐Geschützte 3‐Hydroxypyrrole
Authors: Flitsch Wilhelm , Hohenhorst Manfred 
Published: July 2007

N‐Protected 3‐HydroxypyrrolesStarting from symmetrical imides and (α‐haloacetylmethylene)‐phosphoranes 2, N‐acyl‐3‐hydroxypyrroles 4 have been prepared by an intramolecular Wittig olefination. The deacylation of 4 was proved using 4 b as an example.
Synthese von stereoisomeren 3‐substituierten Cyclobutancarbonsäure‐Derivaten
Authors: V. Dehmlow Eckehard , Schmidt Stefan 
Published: July 2007

Synthesis of Stereoisomeric 3‐Substituted Cyclobutanecarboxylic Acid DerivativesThe preparation of 3‐substituted cyclobutanecarboxylic acids by ring forming malonic ester cycloalkylation/saponification/decarboxylation leads to 50:50 cis/trans mixtures. Only some polar ester derivatives 2 can be separated by chromatographic methods. Catalytic hydrogenation of 3‐substituted cyclobutenecarboxylic acids 3, however, gives the cis acids 4 with 90–95% selectivity. Reduction of the same acids 3 by Zn in aqueous HCl/THF leads to the trans acids 6 with 90–93% selectivity.
Transition metal‐ and acid‐induced transformations of 6‐siloxy‐substituted 5,6‐dihydro‐4H‐1,2‐oxazines: Preparation of pyrroles, nitrones, 1,4‐dicarbonyl compounds and derivatives thereof
Authors: Hippeli Claudia , Zimmer Reinhold , Reißig Hans‐Ulrich 
Published: July 2007

AbstractA variety of 6‐siloxy‐substituted 5,6‐dihydro‐4H‐1,2‐oxazines (abbreviation: 1,2‐oxazines) 1, 3 could be transformed into di‐ and trisubstituted pyrroles 2, 4 by means of molybdenum hexacarbonyl. The mechanism of this deoxygenating ring contraction is discussed. With two bicyclic 1,2‐oxazines an acid‐catalyzed fragmentation affording α‐methylenecycloalkanones 7 has been observed, while other 1,2‐oxazines rearrange in methanolic acid to give nitrones 9, 10. The desilylation of 6‐siloxy‐substituted 1,2‐oxazines 1, 3 employing NEt3 · 3 HF is a very general and smooth process providing 6‐hydroxy‐1,2‐oxazines 11, 12 or their corresponding acyclic tautomers 13, 14 in high yields. For two examples of 11 deoximations by use of formalin could be achieved with moderate efficiency giving 1,4‐dicarbonyl compounds 15.
Investigation of the one‐pot synthesis of N‐(5,6,7,8‐tetrahydro‐7,7‐dimethyl‐2,5‐dioxo‐2H‐1‐benzopyran‐3‐yl‐2,5‐dioxo‐2H‐1‐benzopyran‐3‐yl)benzamide
Authors: Kočevar Marijan , Polanc Slovenko , Verček Bojan , Tišler Miha 
Published: July 2007

AbstractA detailed investigation of the reaction of hippuric acid (2) with dimedone (1) and triethyl orthoformate or other one‐carbon sources in acetic anhydride yielding the benzopyran derivative 3 and many byproducts is described. An explanation of this complex process, several attempts to optimize it, and some new approaches to 3 are given.
Biologically active glycosides from asteroidea, XXV. Glycosphingolipids from the starfish Asterina pectinifera, 2. Structure of three ganglioside molecular species and a homogeneous ganglioside, and biological activity of the ganglioside
Authors: Higuchi Ryuichi , Inagaki Kouji , Natori Takenori , Komori Tetsuya , Kawajiri Shinichi 
Published: July 2007

AbstractThree ganglioside molecular species and a homogeneous ganglioside [GP‐1a (1), GP‐1b (2), GP‐2 (3) and asterinaganglioside A (4)] were obtained from the water‐soluble lipid fraction of the chloroform/methanol extract of the starfish Asterina pectinifera. On the basis of chemical and spectral evidence, the structure of 1–4 were elucidated. GP‐2 (3) was a known ganglioside molecular species, but the other three compounds were new gangliosides. Partial hydrolysis of oligosaccharide moieties with hot water was useful for structure elucidation of the gangliosides. NOE Correlation Spectroscopy (NOESY) was also useful for characterization of the complex sugar moiety. For the isolation of homogeneous ganglioside from the complex molecular species, reversed‐phase HPLC with methanol/ammonia/water as solvent was effective. Moreover, the main ganglioside molecular species, GP‐2 (3), was found to support the survival of cultured cerebral cortex cells, most of which were neuronal cells, of rat fetuses.
Biologically active glycosides from asteroidea, XXVII. Stereochemistry of the C‐17 side chain of 26‐homothornasterol B: Novel triethylaluminum‐promoted rearrangement and alkylation of epoxy alcohols
Authors: Honda Masanori , Igarashi Takashi , Marubayashi Nobuhiro , Komori Tetsuya 
Published: July 2007

AbstractThe absolute configuration of 3,6‐di‐O‐acetyl‐26‐homothornasterol B (3) obtained previously besides the 3,6‐di‐O‐acetyl derivative (2) of (20S,24S)‐24‐ethylthornasterol A by aldol reaction2a) of the mixture of (3S)‐3‐ethyl‐4‐methyl‐2‐(trimethylsiloxy)‐1‐pentene (7) and 3,4‐dimethyl‐2‐(trimethylsiloxy)‐1‐hexene (8) with (+)‐diacetylasterone (1) has been determined by X‐ray structural analysis as (20S,24S,25R)‐3β,6α‐diacetoxy‐20‐hydroxy‐24‐methyl‐26‐homo‐5α‐cholest‐9(11)‐en‐23‐one. On the basis of these results a novel rearrangement and alkylation of the epoxy alcohols 6, 9, 13, and 15 with triethylaluminium have been discovered and investigated. The reaction occurs when the C‐4 position adjacent to the epoxide ring is congested.
Über die Synthese von 2′,3′‐Didesoxy‐3′‐(phosphonomethyl)nucleosiden, Phosphonat‐Analogen von 2′‐Desoxy‐3′‐nucleotiden
Authors: Morr Michael , Ernst Ludger , Schomburg Dietmar 
Published: July 2007

Synthesis of 2′,3′‐Dideoxy‐3′‐(phosphonomethyl)nucleosides, Phosphonate Analogs of 2′‐Deoxy‐3′‐nucleotides1,2‐Di‐O‐acetyl‐5‐O‐benzoyl‐3‐deoxy‐3‐(diethoxyphosphorylmethyl)‐β‐D‐ribofuranose (8) is linked (a) to the protected purine bases ABz, GiB and T, respectively, in the presence of potassium nonaflate and (b) to the silylated pyrimidine bases C, U and UF (= 5‐fluoro‐U) according to the Hilbert‐Johnson method by using stannic tetrachloride. Selective 2′‐O‐deacetylation by hydroxylammonium acetate or hydrazine hydrate employing Ishido's procedure, followed by reaction with phenyl thionochlorocarbonate/4‐(dimethylamino)pyridine, furnishes thionocarbonates 14a–f. These are converted to the deoxy derivatives 15a–f with tributyltin hydride/azobis(isobutyronitrile). For the preparation of the free 2′‐deoxy‐3′‐phosphonic acids 18a–f a special strategy is developed. Hydrolysis of the phosphonic esters is carried out by using bromotrimethylsilane or iodotrimethylsilane, the latter being prepared in situ. 3′‐Deoxy‐3′‐(phosphonomethyl)guanosine (10b1) is described for the first time. The structures of the new compounds follow from their 1H‐, 13C‐ and 31P‐NMR spectra. X‐ray structure analyses were carried out for 8, for 9‐(5‐O‐benzoyl‐3‐deoxy‐3‐diethoxyphosphorylmethyl‐β‐D‐ribofuranosyl)‐6‐hydroxy‐2‐isobutyramidopurin (12b) and its 2,3‐dideoxy analog 15b.