On the synthesis of ecdysone. IV. On insect hormones. The synthesis of the natural skin shedding hormone

Ecdysone ( 9 ), a hormone responsible for the skin shedding process of arthropoda, has been synthesized. (20S)-2β,3β-Diacetoxy-20-formyl-5β-pregn-7-en-6-one was prepared from the corresponding carboxylic acid and converted into ecdysone by a GRIGNARD reaction with 2-methyl-3-butyn-2-ol tetrahydropyran-2-yl ether, followed by hydrogenation of the triple bond, removal of the protecting groups, and hydroxylation in the 14α-position. C-22-isoecdysone was obtained as a by-product.     

Synthesis of ecdysone. 3. On insect hormones. Syntheses of 2-beta, 3-beta, 14-alpha-trihydroxy-6-keto-delta-7-A-B-cis-steroids

The synthesis of the tetracyclic skeleton of ecdysone with correct stereochemistry and substitution is described. 22,25-Didehydroxy-ecdysone and methyl (20S)-2β,3β-dihydroxy-6-oxo-5β-pregn-7-ene-20-carboxylate have been prepared. The latter is a key intermediate in the synthesis of ecdysone.     

Concerning carbon-13 n.m.r. spectroscopy of 5β-hydroxylated phytoecdysones

The ¹³C n.m.r. spectra of the 5β-hydroxylated phytoecdysones polypodine B, muristerone A and kaladasterone are presented and briefly discussed together with the spectrum of makisterone A. Comparisons with previously reported spectra of ecdysone, ecdysterone and poststerone are made and allow a correction for the C-20/C-24 assignment for ecdysone.     

β-Carbolines as agonistic or antagonistic benzodiazepine receptor ligands. 1. Synthesis of some 5-, 6- and 7-amino derivatives of 3-methoxycarbonyl-β-carboline (β-CCM) and of 3-ethoxycarbonyl-β-carboline (β-CCE)

Condensation of diethyl formylamino- or diethyl acetylaminomalonate with 4-, 5- or 6-nitrogramine 1 afforded the diethyl formylamino- or the diethyl acetylamino[(nitroindol)-3-ylmethyl]malonates 2 ; reduction of the nitro group followed by N-formylation or acetylation of the resulting amino compounds 3 , led to the 4-, 5-and 6-acylamino derivatives 4 . Cyclization of 4 in the presence of polyphosphoric esters gave the 3,3-bis(ethoxycarbonyl)-3,4-dihydro-β-carbolines 5 , which underwent lithium chloride/water catalyzed monodeethoxycarbonylation to the corresponding 5-, 6- and 7-acylamino-3-ethoxycarbonyl-β-carbolines 6 , whose acidic hydrolysis led finally to the 5-, 6- and 7-amino-3-ethoxycarbonyl-β-carbolines 9 . The 6-amino compounds 9b-e were obtained also by direct nitration of 3-methoxycarbonyl-β-carboline 7a and of 3-ethoxycarbonyl-β-carboline 7c , followed by the nitro group reduction of the resulting nitro carbolines 8 . Preliminary studies of the binding to rabbit brain benzodiazepine receptor sites indicate compounds 9b and 9c to inhibit the ³H-diazepam binding at 10^?8 M concentrations.     

Reaction of 3-methoxy-17-methylmorphinan-6-one with formaldehyde

Reaction of 3-methoxy-17-methylmorphinan-6-one ( 1 ) and formaldehyde with the presence of calcium hydroxide in aqueous dioxane gave 7,7-bis(hydroxymethyl)-3-methoxy-17-methyl-5-methylenemorphinan-6β-ol ( 2a ). Catalytic reduction of 2a yielded the 5α-methyl compound, 2b . Tosylation of 2a,b followed by lithium triethylborohydride reduction gave either 7α-methyl-6β,7β-oxetanes 4a,b or 7,7-dimethyl-6β-ols 5a,b , depending on reaction conditions. The C-6 ketones 6a,b were prepared by oxidation of 5a,b . One compound in this series, 6a , had antinociceptive activity.     

Microbial carbonylation and hydroxylation of 20(R)-panaxadiol by Aspergillus niger

20(R)-panaxadiol (PD) was metabolised by the fungus Aspergillus niger AS 3.3926 to its C-3 carbonylated metabolite and five other hydroxylated metabolites (1–6). Their structures were elucidated as 3-oxo-20(R)-panaxadiol (1), 3-oxo-7β-hydroxyl- 20(R)-panaxadiol (2), 3-oxo-7β,23α-dihydroxyl-20(R)-panaxadiol (3), 3,12-dioxo- 7β,23β-dihydroxyl-20(R)-panaxadiol (4), 3-oxo-1α,7β-dihydroxyl-20(R)-panaxadiol (5) and 3-oxo-7β,15β-dihydroxyl-20(R)-panaxadiol (6) by spectroscopic analysis. Among them, compounds 2–6 were new compounds. Pharmacological studies revealed that compound 6 exhibited significant anti-hepatic fibrosis activity.     

Copolymeric cyclodextrin polysiloxane stationary phases prepared from 6A,6C- and 6A,6D-dialkenyl-substituted β-cyclodextrin

The syntheses of four new β-cyclodextrin-hexasiloxane copolymers from heptakis(2,3-di-O-methyl)-β-cyclodextrin (2) by multi-step processes are described. 6^A,6^C-Di-O-[p,p'-methylenebis(benzenesulfonyl)]hetakis(2,3-di-O-methyl)β-cyclodextrin (3) , which was prepared by the reaction of 2 with p,p'-methylenebis-(benzenesulfonyl chloride), is a key intermediate for the preparation of permethylated 6^A,6^C-bisalkenyl-β-cyclodextrins 5, 6 , and 9. Permethylated 6^A,6^C-bissulfonate ester 4 , which was obtained from 3 by a methylation reaction under mild conditions, was reacted with sodium allyloxide or sodium ω-undecenyloxide to produce permethylated 6^A,6^C-bisallyl- (or bis-ω-undecenyl)-β-cyclodextrin 5 or 6 or was hydrolyzed with 2% sodium amalgam in methanol to yield diol 7. Compound 7 was oxidized with periodinane, followed by Wittig's reaction with methyltriphenylphosphonium iodide to give permethylated 6^A,6^C-dideoxy-6^A,6^C-dimethylene-β-cyclodextrin (9). Treatment of 2 with p,p'-methylenebis(benzenesulfonyl chloride) or p,p'-biphenyldisulfonyl chloride gave bissulfonate esters 10 or 11 , respectively. Both of them were treated with sodium p-allyloxy-phenoxide in DMF, followed by methylation, to form permethylated 6^A,6^D-di-O-(p-allyloxyphenyl)-β-cyclo-dextrin (16). Bisalkenes 5, 6, 9 and 16 were copolymerized with α,ω-dioctyldecamethylhexasiloxane by a hydrosilylation process to give the cyclodextrin-containing copolymers 17–20.     

Zur Synthese des Ecdysons. II. Mitteilung über Insektenhormone Synthesen von 2β, 3β-Dihydroxy-6-keto-A|B-cis-Steroiden

Experiments towards a synthesis of ecdysone ( 1 ) ([22R]-2β, 3β, 14, 22, 25-pentahydroxy-5β, 14α-cholest-7-en-6-one) have led to 2β, 3β-dihydroxy-6-keto-5α-steroids. These could be epimerized to the corresponding 5β-series. The proposed configurational assignments are supported by physical data and chemical correlation.     

Isotope labelling in ring a of gibberellin a 20

Full assignments of the ¹H-nmr chemical shifts of the ring A protons in gibberellin A₂₀ methyl ester 13-acetate have been made on the basis of ¹H-, ²H- and ¹³C-nmr data of various deuteriated derivatives. These assignments have been used to prove that catalytic deuteriogenation of GA₅-16, 17- epoxide-13-acetate is a syn-addition from the less hindered β-face accompanied by allylic exchange at C-1 giving isotopic labels at the 1β-, 2β- and 3β- positions. The position and stereochemistry of isotopic labelling was confirmed by comparison with an authentic sample of [1β,2β,3β-²H₃] GA₂₀ methyl ester 13-acetate prepared by methods which introduce deuterium stereoselectively at C-1, C-2 and C-3. The preparation of [2α-²H]GA₂₀ and [3α-²H]GA₂₀ is described.     

Synthesis of Sialic Acid Analogues with the Oxime Group at C-4 Or C-5 of KDN 1

Abstract

The readily available methyl (methyl 3-deoxy-5,8:7,9-di-O-isopropylidene-β-D-glycero-D-galacto-2-nonulopyranosid)onate (7) was converted in five synthetic steps into methyl (methyl 4-acetamido-3,4-dideoxy-β-D-glycero-D-talo-2-nonulopyranosid)onate (11). Selective protection of the C-4, C-7, C-8 and C-9 hydroxy groups of methyl (methyl 3-deoxy-8,9-O-isopropylidene-β-D-glycero-D-galacto-2-nonulpyranosid)onate (2) followed by oxidation of the C-5 hydroxy group and then its oximination gave 5-hydroxyimino derivatives (15 and 16).

     

Synthesis and In Vivo antitumor and antiviral activities of 2′-deoxyribofuranosyl and arabinofuranosyl nucleosides of certain purine-6-sulfenamides,sulfinamides and sulfonamides

2′-Deoxyribofuranosyl and arabinofuranosyl nucleosides of certain purine-6-sulfenamides, sulfinamides and sulfonamides have been prepared by sequential amination and controlled oxidation of the corresponding 6-thiopurine nucleosides, and evaluated for antiviral and antitumor activities in mice. Amination of 2′-deoxy-6-thioinosine ( 4a ) and 9-β-D-arabinofuranosyl-6-thiopurine ( 4c ) with chloramine solution gave the corresponding 6-sulfenamides 5a and 5c , respectively, which on selective oxidation with 3-chloroperoxybenzoic acid (MCPBA) gave diastereomeric 9-(2-deoxy-β-D-erythro-pentofuranosyl)purine-6-sulfinamide ( 6a ) and 9-β-D-arabinofuranosylpurine-6-sulfinamide ( 6c ), respectively. However, oxidation of 5a and 5c with excess of MCPBA gave the corresponding 6-sulfonamide derivatives 7a and 7c , respectively. Similar amination of 2′-deoxy-6-thioguanosine ( 4b ), ara-6-thioguanine ( 4d ) and α-2′-deoxy-6-thioguanosine ( 8 ) gave the respective 6-sulfenamide derivatives 5b, 5d and 9 . Controlled oxidation of 5b, 5d and 9 gave (R,S)-2-amino-9-(2-deoxy-β-D-erythro-pentofuranosyl)purine-6-sulfinamide ( 6b ), (R,S)-2-amino-9-β-D-arabinofuranosylpurine-6-sulfinamide ( 6d ) and the α-anomer of ( 6b) (10 ), respectively. The diastereomeric mixture of (R,S )-10 was partially resolved and the structure of S -10 was assigned by single-crystal X-ray diffraction analysis. Oxidation of 5b, 5d and 9 with excess of MCPBA afforded the respective 6-sulfonamide derivatives 7b, 7d and 11 . Nucleosides 5c and 7c were significantly active against Friend leukemia virus in mice, whereas 6c was somewhat less active. Of the 20 nucleosides evaluated, 12 exhibited biologically significant anti-L1210 activity in mice. Nucleosides 6b and 7a at 173 mg/kg/day × 1 showed a T/C of 153, whereas 7d at 800 mg/kg/day × 1 showed a T/C of 153 against L1210 leukemia. The α-nucleoside 9 at 480 mg/kg/day × 1 gave a T/C of 172. A single treatment with 6b, 7a, 7d and 9 reduced the body burdens of viable L1210 cells by more than 99.2%. The antileukemic activity of these novel nucleosides tended to parallel solubility.     

Carbon-13 NMR study of (20,24)-epoxydammarane triterpenes

Assignments of the ¹³C NMR signals of the dammarane triterpenes, 3β,25,30-trihydroxy-(20R,24R)-epoxydammaran-16-one 3,30-diacetate (trevoagenin A diacetate) (2), its 20S-isomer (trevoagenin B diacetate) (3) and their related (20R)-3β,30-diacetoxy-16-oxo-25,26,27-trisnordammarane-24,20-lactone (4) and its 20S-isomer (5) have been achieved. Suitable tetrahydrofuran models have been synthesized in order to aid the ¹³C NMR assignments of the side-chain carbons of the above-mentioned compounds. The remarkable chemical shift differences observed for C-21 and C-22 between each pair of the C-20 epimers (2, 3 and 4, 5) allowed the confirmation of the C-20 stereochemistry of these ocotillol-type dammarane triterpenes.     

The synthesis of 3-deazapyrimidine nucleosides related to uridine and cytidine and their derivatives

Condensation of 2,4-bis(trimethylsilyloxy)pyridine ( 1 ) with 2,3,5-tri-O-benzoyl-D-ribofuranosyl bromide ( 2 ) gave 4-hydroxy-1-(2,3,5-tri-O-benzoyl-β-D-ribofuranosyl)-2-pyridone ( 3 ). Deblocking of 3 gave 4-hydroxy-1-β-D-ribofuranosyl-2-pyridone (3′-deazauridine) ( 4 ). Treatment of 4 with acetone and acid gave 2′,3′-O-isopropylidene-3-deazauridine ( 6 ). Reaction of 4 with diphenylcarbonate gave 2-hydroxy-1-β-D-arabinofuranosyl-4-pyridone-O₂←2′-cyclonucleoside ( 7 ) which established the point of gylcosidation and configuration of 4 . Base-catalyzed hydrolysis of 7 gave 4-hydroxy-1-β-D-arabinofuranosyl-2-pyridone (3-deazauracil arabinoside) ( 12 ). Fusion of 1 with 3,5-di-O-p-toluyl-2-deoxy-D-erythro-pentofuranosyl chloride ( 5 ) gave the blocked anomeric deoxynucleosides 8 and 10 which were saponified to give 4-hydroxy-1-(2-deoxy-β-D-erythro-pentofuranosyl)-2-pyridone (2′-deoxy-3-deazauridine) ( 11 ) and its α anomer ( 9 ). Condensation of 4-acetamido-2-methoxypridine ( 13 ) with 2 gave 4-acetamido-1-(2,3,5-tri-O-benzoyl-β-D-ribofuranosyl)-2-pyridone ( 14 ) which was treated with alcoholic ammonia to yield 4-acetamido-1-β-D-ribofuranosyl-2-pyridone ( 15 ) or with methanolic sodium methoxide to yield 4-amino-1-β-D-ribofuranosyl-2-pyridone (3-deazacytidine) ( 16 ). Condensation of 13 and 2,3,5-tri-O-benzyl-D-arabinofuranosyl chloride ( 17 ) gave the blocked nucleoside 22 which was treated with base and then hydrogenolyzed to give 4-amino-1-β-D-arabinofuranosyl-2-pyridone (3-deazacytosine arabinoside) ( 23 ). Fusion of 13 with 5 gave the blocked anomeric deoxynucleosides 18 and 20 which were deblocked with methanolic sodium methoxide to yield 4-amino-1-(2-deoxy-β-D-erythro-pentofuranosyl)-2-pyridone (2′-deoxy-3-deazacytidine) ( 21 ) and its a anomer 19 . The 2′-deoxy-erythro-pentofuranosides of both 3-deazauracil and 3-deazacytosine failed to obey Hudson's isorotation rule but did follow the “quartet”-“triplet” anomeric proton splitting pattern in the ¹H nmr spectra.     

STUDY ON CATIONIC RING-OPENING COPOLYMERIZATION OF 1,4-ANHYDRO-2,3-DI-O-BENZYL-α-D-RIBOPYRANOSE WITH 1,4-ANHYDRO-2,3-O-ISOPROPYLIDENE-α-D-RIBOPYRANOSE

Cationic ring-opening copolymerization of 1, 4-anhydro-2, 3-O-isopropylidene-α-D-ribo-pyranose (AIRP) with 1,4-anhydro-2,3-di-O-benzyl-α-D-ribopyranose (ADBR) preparedfrom D-ribose was studied. Copolymerization using SbCl_5 or BF_3 OEt_2 as catalyst atlow temperature gave stereoregular (1→4)β-D-ribofuranan (C-1 and C-4 ring cleavagesee Scheme 1) or (1→5) α-D-ribofuranan (C-1 and C-5 ring cleavage) respectively. Theeffects of catalysts, reaction time and temperatures on yield and stereoregularity of the ob-tained polymers were studied. Polymers were characterized by molecular weight, ~1HNMR,~(13)CNMR and optical rotation.     

A novel fragmentation of trimethylsilyl ethers of 3β-hydroxy-Δ5-steroids

An ion formed by loss of 56 mass units from the molecular ion is often seen in mass spectra of trimethylsilyl ethers of C₁₉ and C₂₁ steroids having a 3β-hydroxy-Δ⁵ structure and an oxo group at C-17 or C-20. The nature of this fragment was investigated by the use of perdeuteriotrimethylsilyl ether derivatives and of [4-¹⁴C], [3-¹⁸O], [4,4-²H₂] and [2,2,4,4-²H] labelled derivatives of 3β-hydroxy-5-androsten-17-one and 3β-hydroxy-5-pregnen-20-one. Evidence is presented to show that the neutral fragment of mass 56 is composed of carbon atoms 1, 2 and 3, the oxygen at C-3 and four hydrogen atoms. During the fragmentation process, the trimethylsilyl group and one of the hydrogens at C-2 are transferred to the fragment that carries the charge.     

Synthesis of 2-(β-D-ribofuranosyl)pyrimidines,A new class of C-nucleosides

A new C-glycosyl precursor for C-nucleoside synthesis, 2,5-anhydroallonamidine hydrochloride ( 4 ) was prepared and utilized in a Traube type synthesis to prepare 2-(β-D-ribofuranosyl)pyrimidines, a new class of C-nucleosides. The anomeric configuration of 4 was confirmed by single-crystal X-ray analysis. Reaction of 4 with ethyl acetoacetate gave 6-methyl-2-(β-D-ribofuranosyl)pyrimidin-4-(1H)-one ( 5 ). Reaction of 4 with diethyl sodio oxaloacetate gave 2-(β-D-ribofuranosyl)pyrimidin-6(1H)-oxo-4-carboxylic acid ( 6 ). Esterification of 6 with ethanolic hydrogen-chloride gave the corresponding ester 7 which when treated with ethanolic ammonia gave 2-(β-D-ribofuranosyl)pyrimidin-6(1H)-oxo-4-carboxamide ( 8 ). Condensation of 2,5-anhydroallonamidine hydrochloride ( 4 ) with ethyl 4-(dimethylamino)-2-oxo-3-butenoate ( 9 ), gave ethyl 2-(β-D-ribofuranosyl)pyrimidine-4-carboxylate ( 10 ). Treatment of 10 with ethanolic ammonia gave 2-(β-D-ribofuranosyl)pyrimidine-4-carboxamide ( 11 ). Single-crystal X-ray analysis confirmed the β-anomeric configuration of 11. Acetylation of 11 followed by treatment with phosphorus pentasulfide and subsequent deprotection with sodium methoxide gave 2-(β-D-ribofuranosyl)pyrimidine-4-thiocarboxamide ( 14 ). Dehydration of the acetylated amide 12 with phosphorous oxychloride provided 2-(β-D-ribofuranosyl)pyrimidine-4-carbonitrile ( 15 ). Treatment of 15 with sodium ethoxide gave ethyl 2-(β-D-ribofuranosyl)pyrimidine-4-carboximidate ( 16 ), which was converted to 2-(β-D-ribofuranosyl)pyrimidine-4-carboxamidine hydrochloride ( 17 ) by treatment with ethanolic ammonia and ammonium chloride. Treatment of 16 with hydroxylamine yielded 2-(β-D-ribofuranosyl)pyrimidine-4-N-hydroxycarboxamidine ( 18 ). Treatment of 2-(β-D-ribofuranosyl)pyrimidine-4-carboxamide ( 11 ) with phosphorus oxychloride gave the corresponding 5′-phosphate, 19 , Coupling of 19 with AMP using the carbonyldiimidazole activation procedure gave the corresponding NAD analog, 2-(β-D-ribofuranosyl)pyrimidine-4-carboxamide-(5′ ? 5′)-adenosine pyrophosphate ( 20 ).     

Nine sesquiterpenes from Solanum torvum

Three new sesquiterpenes, namely 3β,11-dihydroxy-4,14-oxideenantioeudesmane (1), 1β,10β,12,14-tetrahydroxy-allo-aromadendrane (2) and 1β,10β,13,14-tetrahydroxy-allo-aromadendrane (3), along with six known sesquiterpenes (4–9), were isolated from the roots of Solanum torvum. Compound 4 and 5 are epimers, their main difference lies in the C-11 configulation. Normally, epimers do not make a huge difference in C NMR spectra, but in this kind of structure of A, B, C rings, and C ring is sterically strained structure, stericall effects influence strongly the ¹³C NMR chemical shifts, when C-11 configulation changed, it makes a huge difference in the three ring of structure, such as C-6, C-7, C-11. New compound 2 and 3 are epimers and similar to compound 4 and 5, their just increase a hydroxy in C-1 and have a same regular pattern in C NMR spectra, otherwise, compound 5 was firstly confirmed by single-crystal X-ray diffraction.     

PREPARATION AND STRUCTURE OFFIVE DERIVATIVES OFβ-(1→3)-D-GLUCAN ISOLATED FROM PORIA COCOS SCLEROTIUM*

A new solvent of cellulose (1.5 mol/L NaOH/0.5 mol/L urea aqueous solution) was used as one of the homogeneous reaction media of polysaccharides for methylation, hydroxyethylation and hydroxypropylation. A water insoluble β-(1→3)-D-glucan, sample PCS3-Ⅱ, isolated from fresh sclerotium of Poria cocos was sulfated in dimethyl sulfoxide (Me2SO), carboxymethylated in NaOH, isopropanol solution, as well as methylated, hydroxyethylated and hydroxypropylated in the new solvent system, respectively, to obtain five water-soluble derivatives coded as S-PCS3-Ⅱ, C-PCS3-Ⅱ, M-PCS3-Ⅱ, HE-PCS3-Ⅱand HP-PCS3-Ⅱ. Their chemical structure and distribution of substitution were characterized by infrared spectroscopy (IR), elementary analysis (EA), ^1H-NMR, ^13C-NMR, 2D-COSY, 2D-TOCSY and 2D-^1H-detected ^1H ^13C HMQC spectra. The results reveal that the relative reactivity of hydroxyl groups of the β(1→3)-D-glucan is in the order C-6 ＞ C-4 ＞ C-2 on the whole. The substitution of the samples S-PCS3-Ⅱ, C-PCS3-Ⅱ and M-PCS3-Ⅱ occurred mainly at C-6 position and secondly at C-4 and C-2 positions, and that of HE-PCS3-Ⅱ occurred at C-6 and C-4 positions and of HP-PCS3-Ⅱ almost completely occurred at C-6 position. The degrees of substitution (DS) obtained from ^13C-NMR range from 0.23 to 1.27. The water solubility of the derivatives is in the order S-PCS3-Ⅱ ＞ C-PCS3-Ⅱ ＞ M-PCS3-Ⅱ ＞ HE-PCS3-Ⅱ ＞ HP-PCS3-Ⅱ. This work provides a novel and nonpolluting process for the methylation, hydroxyethylation and hydroxypropylation of β-(1→3)-D-glucan.     

Synthesis of certain 3-alkoxy-1-β-D-ribofuranosylpyrazolo[3,4-d]pyrimidines structurally related to adenosine,inosine and guanosine

Several 3-alkoxysubstituted pyrazolo[3,4-d]pyrimidine ribonucleosides structurally related to adenosine, inosine and guanosine have been prepared by the direct glycosylation of preformed aglycon precursor containing a 3-alkoxy substituent. Ring closure of 5(3)-amino-3(5)-ethoxypyrazole-4-carboxamide ( 6b ) with either formamide or potassium ethyl xanthate gave 3-ethoxyallopurinol ( 7b ) and 3-ethoxy-6-thioxopyrazolo[3,4-d]-pyrimidin-4(5H,7H)-one ( 10 ), respectively. Methylation of 10 gave the corresponding 6-methylthio derivative 15 . Similar ring annulation of 5(3)-methoxypyrazole-4-carboxamide ( 6a ) with formamide afforded 3-methoxyallopurinol ( 7a ). Treatment of 5(3)-amino-3(5)-methoxypyrazole-4-carbonitrile ( 5a ) with formamidine acetate furnished 4-amino-3-methoxypyrazolo[3,4-d]pyrimidine ( 4 ). High-temperature glycosylation of 7b with 1-O-acetyl-2,3,5-tri-O-benzoyl-D-ribofuranose in the presence of boron trifluoride etherate gave a 2:1 mixture of N-1 and N-2 glycosyl blocked nucleosides 11b and 13b . Deprotection of 11b and 13b with sodium methoxide gave 3-ethoxy-1-β-D-ribofuranosylpyrazolo[3,4-d]pyrimidin-4(5H)-one ( 12b ) and the corresponding N-2 glycosyl isomer 14b , respectively. Similar glycosylation of either 4 or 7a , and subsequent debenzoylation gave exclusively 4-amino-3-methoxy-1-β-D-ribofuranosylpyrazolo[3,4-d]pyrimidine ( 9 ) and 3-methoxy-1-β-D-ribofuranosylpyrazolo[3,4-d]pyrimidin-4-(5H)-one ( 12a ), respectively. The structural assignment of 12a was made on the basis of single-crystal X-ray analysis. Application of this general glycosylation procedure to 15 gave the corresponding N-1 glycosyl derivative 16 as the sole product, which on debenzoylation afforded 3-ethoxy-6-(methylthio)-1-(3-D-ribofuranosylpyrazolo[3,4-d]pyrimidin-4(5H)-one ( 17 ). Oxidation of 16 and subsequent ammonolysis furnished the guanosine analog 6-arnino-3-ethoxy-1-β-D-ribofuranosylpyrazolo[3,4-d]-pyrimidin-4(5H)-one ( 19 ). Similarly, starting from 3-methoxy-4,6-bis(methylthio)pyrazolo[3,4-d]pyrimidine ( 20 ), 6-amino-3-methoxy-1-β-D-ribofuranosylpyrazolo[3,4-d]pyrimidin-4(5H)-one ( 23 ) was prepared.     

Zur lokalisierung funktioneller gruppen mit hilfe der massenspektrometrie—VIII : 6-hydroxy-androstan-3,17-dione und 6,17β-dihydroxy-androstan-3-one

5β-androstan-3-ones carrying a 6α-OH group show in their mass spectra a key-ion indicating the loss of water and C-1 to C-4 as C₄H₅O? particle. 6β-OH isomers lose instead C-1 to C-4 in form of C₄H₇O?.In 6α-hydroxy-androstan-3-ones differentiation between the connection of the A/B-ring system is possible, because in 5α-isomers the loss of C-3 to C-7 occurs as a C₅H₆O₂ particle, while the 5β-isomers lose the same C atoms as a C₅H₇O? unit.Compounds with a 6β-OH group in an A/B trans connected ring system show a tendency for thermal water elimination. After rearrangement of the double bond in 4,5 position the typical fragments for 3-keto-Δ⁴-steroids are obtained.Occasionally a strong influence of a 6-OH group on fragmentation reactions in the D-ring system is observed: The presence of a 6α-OH group in an androstan-3,17-dione enhances the loss of C-16 and C-17 in the form of acetaldehydenol. Also the connection of the A/B-ring system may have a considerable influence on this type of reaction: In 6,17β-dihydroxy-androstan-3-ones only by trans connection of the A/B-ring system, C-16 and C-17 are lost with high probability after water elimination.