Tetrahedron: Asymmetry

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Tetrhedron: Asymmetry 22 (2011) 740 744 Contents lists vilble t Scienceirect Tetrhedron: Asymmetry journl homepge: www.elsevier.

Lichtenthler Clemens-Schöpf-Institut für rgnische Chemie und Biochemie, Technische Universität rmstdt, Petersenstrße 22, -64287 rmstdt, Germny rticle info bstrct Article history: Received 8 Mrch 2011

1 Tetrhedron: Asymmetry 22 (2011) Contents lists vilble t Scienceirect Tetrhedron: Asymmetry journl homepge: Convenient ccess to 4--glycosylted 1,5-nhydro--fructoses vi discchride-derived 2-hydroxyglycl esters q Toshio kgw, Frieder W. Lichtenthler Clemens-Schöpf-Institut für rgnische Chemie und Biochemie, Technische Universität rmstdt, Petersenstrße 22, rmstdt, Germny rticle info bstrct Article history: Received 8 Mrch 2011 Accepted 18 Mrch 2011 Avilble online 19 April 2011 Efficient six-step protocols re described for the conversion of common discchrides, such s mltose, cellobiose, or lctose, into the corresponding 4--glycosyl-1,5-nhydro--fructoses. verll yields of 40 45% re fvorbly compred to the lterntive eleven-step procedure from their monoscchride components (15%). Ó 2011 Elsevier Ltd. All rights reserved. 1. Introduction Thirty yers go, nd seven yers before being encountered s nturlly occurring monoscchride, 2 1,5-nhydro--fructose 1 ws synthesized from -glucose in six-step sequence, 3 the first three steps comprising of the genertion of its 2-hydroxygluclester 2, 4 the others being the selective hydroxylminolysis 5 of the enol ester group 2?3, Zemplén de--cyltion, nd deoximtion (3?4?1) (Scheme 1). Since then, vrious other enzymtic 6 nd H chemicl 7 pproches to 1,5-nhydro--fructose, usully chrcterized s the monohydrte, hve been developed, mong them the direct low-temperture decetyltion of the cetylted hydroxyglucl ester 2 (R = Ac). 3b,7b Either of these simple pproches to 1,5-nhydro--fructose, should in principle be pplicble to ny of the common discchrides, conjecture which hs lredy been verified 8 by conversion of mltose, cellobiose, nd lctose, vi their 2-hydroxyglycl esters 5 5c into the respective perbenzoylted 4--glycosyl-1,5-nhydrofructoses 6 6c, with yields in the 70% rnge for the four steps involved 8 (Scheme 2). The lctose-derived 6c ws even deoximted to the respective, highly crystlline ulose monohydrte steps ~70% R -Glucose R 2 R R Me / MeH H 2 H 0 o C (R = Ac) Me/ MeH q Prt 45 of the series, Sugr-erived Building Blocks ; for Prt 44, see Ref. 1. Corresponding uthor. Tel.: E-mil ddress: lichtenthler@chemie.tu-drmstdt.de (F.W. Lichtenthler). H R H 1 R R MeCH / H + 4 H 3 R = Bz 3b R = Ac 4 R = H Scheme 1. Chemicl pproches to 1,5-nhydro--fructose. R Bz Bz Bz Mltose Cellobiose Lctose Bz 6-c Bz Bz 7 H Bz Bz H 2 H H H R Bz 5-c Bz Bz : R = αbz 4 Glc b : R = βbz 4 Glc c : R = βbz 4 Gl Scheme 2. iscchride-derived 1,5-nhydrofructose derivtives /$ - see front mtter Ó 2011 Elsevier Ltd. All rights reserved. doi: /j.tetsy

2 T. kgw, F. W. Lichtenthler / Tetrhedron: Asymmetry 22 (2011) Apprently unwre of this expedient, lrge scle dptble ccess to 4--glycosylted 1,5-nhydrofructoses, recently, Agoston et l. ptented 7b nd published 9 nother pproch comprising of the glycosyltion of bicyclic 1,5-nhydrofructose derivtive with glycosyl trichlorcetimidtes, n inconvenient route due to the 11 steps required, three for the donor subtrte; 10 five for the cceptor; 7c nd nother three for the trgets 9 with overll yields of round 15%. ue to potentil medicl pplictions, 11 interest in 1,5-nhydro- -fructose hs substntilly incresed recently, n ppel tht extends to its glycosylted nlogues, in s much s (1?3)-1,5- nhydrofructose prepred by enzymtic trnsglucosyltion ws deemed suitble for conjugtion with proteins 12 nd s ntioxidnt food dditives. 13 Since their genertion vi 2-hydroxyglucl esters from the common discchrides ws considered to be significntly more simple thn glycosyltions of 1,5-nhydrofructose derivtives, we hve resumed our erlier work 8 nd herein describe the strightforwrd deprotection of the 4--glycosyl-1,5-nhydrofructose oximes 6 6e to the underlying free discchrides. 2. Results nd discussion In view of the most expedient ccess to 1,5-nhydro--fructose vi de--cetyltion of 2-cetoxy--glucl tricette 2?1, 3b,7b it ppered obvious to generte glycosylted nlogues of 1 from discchride-derived 2-hydroxyglucl esters. When pplied to the mltl- nd cellobil-derived 5d nd 5e, the rection produced severl products in ddition to the desired 4--glucosyl-1,5-nhydrofructoses 9f nd 9g; mong them, substntil mounts of -glucose, obviously originting from bse induced b-elimintion, rection redily occurring with 2-hydroxyglycl esters under mild bsic conditions. 3,5 As chromtogrphic purifiction proved quite lborious, this ccess ws not elborted. In the cse of discchrides crrying the glycosyl residue t positions other thn -4, however, such s the (1?6)-interscchridic isomltose, gentiobiose, or melibiose, the low-temperture decyteltion procedure my well be used to efficiently generte 1,5-nhydrofructoses with --glucosyl-, b--glucosyl or b-glctosyl residues t -6. Appliction of the three-step sequence hydroxylminolysis, de- -cyltion nd deoximtion to ny of the discchride-derived 2- hydroxyglucl esters 5 5e proceeded in preprtively strightforwrd mnner. The estblished hydroxylminolysis protocol, 5,8 3,5-4 molr hydroxylmine hydrochloride in pyridine t mbient temperture (24 h) or t 70 C (4 h), smoothly fforded the glycosyl-(1?4)-1,5-nhydrofructose E-oximes 6 6e isolble in excellent yields of 85 90%. Tht these products invribly hve their H group oriented towrd the less congested, pronomeric center, tht is, re E- oximes s indicted in the formule, follows, mong other indictions, from the chemicl shift for their equtoril H-1, which ppers within the sme nrrow rnge s in the cylted 1,5- nhydrofructoses 3 nd 3b (Tble 1), tht is, show the sme significnt downfield shift cused by the nerly coplnr H group s seen. 1,14 The relese of the free glycosyl-(1?4)-1,5-nhydrofructoses 9f 9h from their oximes proceeded in the expected mnner: de-cyltion under Zemplén conditions (Me/MeH, rt, h) smoothly fforded the respective oximes 8f 8h, ech isolted nd chrcterized s E/Z-mixtures, since the bsic conditions obviously induced E?Z equilibrtions. The E-isomers thereby constituted the min components in up to 5:1 preference, yet none crystllized s ws the cse with the monoscchridic 1,5-nhydro--fructose E-oximes 4. 3 Although seprble by chromtogrphy due to the sufficiently different R f vlues, the E/Z-oxime mixtures 8f 8h were directly subjected to trnsoximtion by exposure, in n cetonitrile solution, to excess cetldehyde in the presence of 1 M HCl (6 h, rt). The resulting glycosyl-(1?4)- 1,5-nhydrofructoses 9f 9h (Scheme 3) were secured in the form of glsses or fluffy solids by freeze-drying their Sephdex-purified queous solutions, with yields being in the 75% rnge only, due to the somewht elborte purifiction procedure. Anlyticl vlues were uniformly within the cceptble limits for the monohydrte (C 12 H H 2 ) or 2,2-dihydroxy forms, s indicted in the formule. Unequivocl structurl proof followed from their 1 H nd 13 C MR spectr of 9f 9h in 2 (pertinent dt shown in Tble 2) which conclusively reveled the signl nd coupling ptterns expected for their 4--glycosyl nd 1,5-nhydrofructose portions. Moreover, our MR dt for the glycosyl-b(1?4)-1,5-nhydrofructose 9g nd 9h corresponded well with those obtined for 9g nd 9f prepred vi glycosyltion of 4-H-free 1,5-nhydrofructose derivtive, 9 lbeit there re minor shift differences. The micronlyticl dt, however, re distinctly different. While our glycosyl-1,5-nhydrofructoses 9f 9h invribly give stisfctory C, H vlues for the monohydrte or 2,2-dihydroxy forms, the respective Agoston et l. 9 products represent dihydrtes, s evidenced by essentilly perfect nlyticl vlues for C 12 H H 2 (or C 12 H H 2 in their nottion), thereby fostering reservtions s to the integrity of these products. Similr reservtions lso pply to two 4--glycosyl-1,5-nhydro-tgtoses prepred in the sme wy. 9 They nlyze for monohydrtes, wheres 1,5-nhydro--tgtose exhibits pronounced tendency to dpt the 2-crbonyl form in queous solution nd in the solid stte. 6d,14 A clrifiction of these inconsistencies ppers to be de rigueur. 3. Conclusion Efficient, lrge scle-dptble protocols re presented for the conversion of common bulk discchrides such s mltose, cellobiose, or lctose vi their 2-hydroxyglycl esters into the respective glycosyl-(1?4)-1,5-nhydrofructoses. The yields ttinble re in the 40 45% rnge for the six steps involved, which compres fvorbly with the 15% yield over the eleven step procedure, 9 when cquiring these products from glucose nd fructose, respectively. Tble 1 Pertinent 1 H MR dt (500 MHz) for cylted 1,5-nhydro--fructose E-oximes nd its 4--glycosyl nlogs Compound R R 0 Solvent H-1e H-1 H-3 H-4 H H-1 0 J 1,1 J 3,4 J 4,5 J 1 0,2 0 Ref. 3 Bz Bz MS-d CCl b 6 b GlcBz 4 Bz CCl b b bglcbz 4 Bz CCl c b bglbz 4 Bz CCl b Ac Ac MS-d b 6d GlcAc 4 Ac CCl e bglcac 4 Ac CCl Abbrevitions s in Scheme 3. b Previously, 8 only 100 MHz dt were given.

3 742 T. kgw, F. W. Lichtenthler / Tetrhedron: Asymmetry 22 (2011) Mltose Cellobiose Lctose 3 steps 75-80% R' R R R 5-e H 2 H pyridine 85-90% R' R R 6-e H R R' Bz αglcbz 4 b Bz βglcbz 4 c Bz βglbz 4 d Ac αglcac 4 e Ac βglcac 4 Me MeH H R H H H 9f-h MeCH H + R H H 8f-h H H H H H f: R = H ; H H g: R = H H H ; h: R = H H α--glc β--glc β--gl Scheme 3. Six-step conversion of common discchrides into 4--glycosyl-1,5-nhydrofructoses. Tble 2 Significnt 1 H nd 13 C MR dt (500 resp. 75,5 MHz in 2 ) for the monohydrtes of 1,5-nhydro--fructose nd its 4--glycosyl derivtives 9f 9h Signls 1 3b 9f 9g 9h H-1e H H H H J 1, J 3, J 4, J 1 0 0, C C C C C C C ot unequivocbly ssignble due to complex overlp of multiplets. 4. Experimentl 4.1. Generl Melting points were determined with Bock hot-stge microscope nd re uncorrected. pticl rottions were mesured t 20 C with Perkin-Elmer 241 polrimeter using cell of 1 dm pth length. 1 H nd 13 C MR spectr were recorded on Bruker ARX 300 nd Avnce 500 instruments. Mss spectr were cquired on Vrin MAT 311 spectrometer, micronlyses on Perkin-Elmer 240 elementl nlyzer. Anlyticl thin lyer chromtogrphy (TLC) ws performed on Kieselgel 60 F 254 plstic sheets (Merck, rmstdt) with detection by UV light or by sprying with 50% sulfuric cid nd chrring t 140 C for 5 min. Column chromtogrphy ws performed on Silic Gel 60 (Merck, ppm) using the specified eluents ,6-i--cetyl-4--(2,3,4,6-tetr--cetyl--glucopyrnosyl)-1,5-nhydro--fructose E-oxime 6d To solution of H 2 HHCl (2.4 g, 35 mmol) in pyridine (100 ml) were dded 6.2 g (10 mmol) of 2-cetoxymltl hexcette 5d 15 nd the mixture ws stirred t mbient temperture until the educt hd disppered (c. 24 h, R f = 0.33?0.21 in 2:1 toluene EtAc). Most of the solvent ws removed by evportion in vcuo (40 C bth temperture) nd the residue ws dissolved in mixture of wter nd CHCl 3 (150 ml ech), followed by seprtion nd extrction of the wter lyer with CHCl 3 (2 100 ml). The combined CHCl 3 extrcts were wshed with ice-cold 1 M HCl solution nd wter, dried (MgS 4 ), nd tken to dryness in vcuo. The sirupy residue crystllized on triturtion with EtH: 4.75 g (81%) of 6d s colorless needles (2 crops); mp C; ½Š 20 ¼ 61:4 (c 1.0, CHCl 3); 1 H MR (500 MHz, CCl 3 ): d (six 3H-s, 6 Ac), 3.58 (ddd, 1H, H-5), 3.85 (dd, 1H, H-4), 3.96 (ddd, 1H, H-5 0 ), 4.01 nd 4.17 (two 1H-dd, 6-H 2 ), 4.11 nd 4.31 (two dd, 6 0 -H 2 ), 4.20 (1H-d, H-1), 4.81 (1H-dd, H-2 0 ), 4.85 (1H-dd, H-1b), 4.98 (1H-dd, H-4 0 ), 5.27 (1H-d, H-3), 5.31 (1H-dd, H-3 0 ), 5.41 (1H-d, H-1 0 ), 8.23 (1H-s, H); J 1,1 = 16.5, J 3,4 = 4.5, J 4,5 = 7.7, J 5,6 = 2.3 nd 4.5, J 6,6 = 12.4; J 1 0,2 = 4.0, J 0 2 0,3 = 10.4, 0 J 3 0,4 = J 0 4 0,5 = 9.6, J 0 5 0,6 = 2.7 nd 6.3, J 0 6 0,6 = 12.1 Hz. 13 C MR 0 (75.5 MHz, CCl 3 ): d (6 AcCH 3 ), 62.1 nd 64.1 (C-6, C- 6 0 ), 63.1 (C-1), (C-5, C-2 0 C-4 0 ), 72.1 (C-3), 75.4 nd 77.1 (C-4, C4 0 ), 95.8 (C-1 0 ), (C-2). Anl. Clcd for C 24 H (591.51): C, 48.73; H, 5.62;, Found: C, 48.61; H, 5.57;, ,6-i--cetyl-4--(2,3,4,6-tetr--cetyl-b-glucopyrnosyl)-1,5-nhydro--fructose E-oxime 6e Hydroxylminolysis of 2-cetoxy-cellobil hexcette 5 16 (10.2 g, 16.4 mmol) ws effected by stirring in pyridine (100 ml) contining H 2 HCl (10.0 g, 0.15 mol) for bout 24 h t room temperture (R f = 0.27?0.16 in 2:1 toluene EtAc). Work-up s described bove for 6d gve sirupy residue crystllizing from

4 T. kgw, F. W. Lichtenthler / Tetrhedron: Asymmetry 22 (2011) EtH: 8.24 g (85%) of 6e in two crops; colorless needles of mp C; ½Š 20 ¼ 25:9 (c 1.0, CHCl 3); 1 H MR (500 MHz, CCl 3 ): d (six 3H-s, 6 Ac-CH 3 ), 3.51 (1H-ddd, H-5), 3.78 (1H-ddd, H-5 0 ), 3.83 (1H-dd, H-4), 4.09 nd 4.11 (two 1H-dd, H-6 nd H- 6b), 4.26 (1H-d, H-1), 4.30 nd 4.31 (two 1H-dd, H-6b nd H- 6b 0 ), 4.70 (1H-d, H-1 0 ), 4.90 (1H-d, H-1b), 4.97 (1H-dd, H-2 0 ), 5.08 (1H-t, H-3 0 ), 5.19 (1H-t, H-4), 5.73 (1H-d, H-3), 8.71 (1H-s, H); J 1,1 = 16.4, J 3,4 = 4.4, J 4,5 = 8.1, J 5,6 = 2.6 nd 4.9, J 6,6 = 11.9, J 1 0,2 = 8.1, J 0 2 0,3 = J 0 3 0,4 = J 0 4 0,5 = 9.5, J 0 5 0,6 = 4.9 nd 6.1, J ,6 = 12.0 Hz. 13 C MR (75.5 MHz, CCl 3 ): d (AcCH 3 ), 61.8, 63.1 nd 63.4 (C-1, C-6, C-6 0 ), 71.0, 71.4, 72.1, 72.8 (C-3, C-2 0, C-3 0, C-5 0 ), 76.5 (C-5), 79.0 (C-4), (C-1 0 ), (C-2). Anl. Clcd for C 24 H (591.51): C, 48.73; H, 5.62;, Found: C, 48.69; H, 5.51;, (--Glucopyrnosyl)-1,5-nhydro--fructose E/Zoxime 8f Commercil 30% methnolic sodium methoxide (1.3 ml) ws dded with stirring to solution of mltose-derived oxime hexcette 6d (3.75 g, 6.3 mmol) in methnol (150 ml) TLC monitoring fter bout 2 h with 8:5:1 iprh/etac/wter showed complete conversion of the educt into n pproximte 2.5:1 mixture of E/Z-isomers ( 1 H MR) of R f = 0.54 (tenttively the E-isomer) nd 0.27, respectively. The solution ws then deionized by briefly stirring with Amberlite 120 (H + form) filtrtion nd wshing of the resin with methnol. The filtrte nd wshings were subjected to brief chrcol tretment followed by n in vcuo removl of the solvent, finlly t 0.1 Torr: 1.78 g (83%) of E/Z-8f s fluffy solid. 1 H MR (500 MHz, 2 ): 5.20 (1H-d, J 1 0,2 0 = 3.8 Hz, H-10 ), 5.12 (1H-d, J 3,4 = 3.8 Hz, H-3), 4.90 nd 4.20 (two 1H-d, J 1,1 = 16.1 Hz, 1-Hb, nd 1-H) for the mjor, conceivbly the E-isomer; other signls not interpreted due to E/Z-mixture nd extensive overlp. Anl. Clcd for C 12 H (339.29): C, 42.48; H, 6.24;, Found: C, 42.29; H, 6.17;, The E/Z-isomeric oximes, due to sufficiently different mobilities (R f = 0.54 nd 0.27, resp.), my be seprted by chromtogrphy on silic column, yet the pure isomers tend to equilibrte upon removl of the elution solvents. Thus, the E/Z-mixture ws subjected directly to deoximtion (?9f, see below) (--Glucopyrnosyl)-1,5-nhydro--fructose monohydrte 9f Acetldehyde (0.57 ml, 10 mmol) nd 1 M HCl (5 ml) ws dded to suspension of the E/Z-oxime mixture 8f (1.20 g, 3.5 mmol) in cetonitrile (25 ml), followed by stirring t mbient temperture for 5 h. ilution with wter (10 ml), neutrliztion by briefly stirring with bsic resin, in vcuo evportion to smll volume (2 ml), elution from n LH 20 Sephdex column (25 2 cm) with wter, nd lyophiliztion of the product-crrying elutes gve the discchride monohydrte 9f s colorless fom (630 mg, 74%). 1 H MR (500 MHz, 2, 5 h fter solution for equilibrtion): d 5.29 (1H-d, J 1 0,2 0 = 3.8 Hz, H-10 ), 3.80 nd 3.68 (two 2Hm, 6-H 2,6 0 -H 2, 3.71 nd 3.42 (two 1H-d, J 1,1 = 12.4 Hz, H-1b, nd H1), 3.60 (br m, H-4, H-5, H-2 0, H-3 0 ), 3.50 (14-d, J 3,4 = 8.1 Hz, H-3), 3.35 (1H-m, H-4 0 ). 13 C MR (75.5 MHz, 2 ): d 99.7 (C-1 0 ), 80.1 (C-5), 78.9 nd 78.7 (C-3, C-4), 73.6 (C-3 0 ), 73.0 (C-1), 72.4 nd 72.2 (C-2, C-5 0 ), 70.1 (C-4 0 ), 61.8 nd 61.3 (C-6, C-6 0 ). Anl. Clcd for C 12 H H 2 (342.30): C, 42.10; H, Found: C, 41.82; H, e--benzoyltion of mltose-derived oxime hexbenzote 6 (?8) nd subsequent deoximtion with cetldehyde in procedure identicl to the glctosyl nlogue 6c (see Section 4.7) fforded 9f in 66% yield (b--Glucopyrnosyl)-1,5-nhydro--fructose monohydrte 9g To stirred solution of cellobiose-derived oxime hexcette 6e (4.15 g, 7.0 mmol) in dry methnol (200 ml) ws dded 2.0 ml of commercil 30% (5.56 M) methnolic sodium methoxide solution nd the mixture ws stirred t mbient temperture. After bout 3 h, (TLC monitoring in 5:3:1 i-prh/etac/wter reveled products t R f = 0.62 nd 0.71) the solution ws deionized with smll mount of Amberlite IR 120 (H + form) nd, subsequently, subjected to chrcol tretment. Removl of the solvent in vcuo gve the sirupy 8g (2.1 g, 88%) s n pproximte 3:1 mixture ( 1 H MR) of E/Zisomers. (mjor) 3.8 Hz-d for H-3 t 5.16, 15.5 Hz-d for H-1b t 4.95 ppm; minor: H-3 s 3.4 Hz-d t 5.02, H-1b s 15.9 Hz-d t 4.93 ppm). eoximtion of the E/Z-mixture 8g (2.0 g, 5.9 mmol) ws effected by stirring in cetonitrile (40 ml) with cetldehyde (1 ml, 17.5 mmol) nd M HCl (8 ml) t rt for 5 h, followed by dilution with wter (15 ml) neutrliztion by briefly stirring with bsic resin, nd in vcuo evportion to give sirup. Purifiction by elution from silic gel column (2 20 cm) with 7:3 n-propnol wter nd in vcuo evportion of the product-crrying elutes gve 1.27 g (63 %) of 9g s fluffy solid. ½Š 20 ¼ 21:2 (c 1.0, wter); 1 H MR (500 MHz, 2, 3 h fter dissolution): d 4.40 (1H-d, J 1 0,2 = 7.9 Hz, 0 H-10 ), 3.90 nd 3.75 (two 2H-m, 6-H 2,6 0 -H 2 ), 3.70 nd 3.42 (two 1H-d, J 1,1 = 12.1 Hz, H-1b nd H-1), 3.60 (2H-m, H-3, H-4), 3.40 (br 4H-m, H-5, H-3 0 H-5 0 ), 3.26 (1H-m, H- 2 0 ). 13 C MR ( 2 ): d (C-1 0 ), 93.1 (C-2), 79.7 nd 79.4 (C-3, C-4), 76.2 (C-3, C-5 0 ), 75.7 (C-5), 74.0 (C-2 0 ), 71.8 (C-1), 70.3 (C- 4 0 ), 60.9 (C-6, C-6 0 ). Anl. Clcd for C 12 H H 2 (342.30): C, 42.10; H, Found: C, 42.02; H, Whilst these 1 H nd 13 C MR dt correspond firly well with those reported by Agoston et l. 9 (there were some minor chemicl shift differences) their micronlyticl dt (found: 9 C, 40.09; H, 6.65) do not, s these re distinctly too low; however, they mtch those required for C 12 H H 2 (sum formul given in Ref. 9), which fctully is dihydrte (clcd for C 12 H H 2 : C, 40.00; H, 4.71). These peculir incongruities remin to be clrified. e--benzoyltion of oxime hexbenzote 6b, directly followed by deoximtion in procedure s detiled for the glctosyl nlogue (see Section 4.7) fforded 9f in 61% yield (b--Glctopyrnosyl)-1,5-nhydro--fructose monohydrte 9h Lctose-derived oxime hexbenzote 6c (2.40 g, 2.5 mmol) ws stirred in 30 ml of 0.1 M methnolic Me solution (prepred by dding 5.4 ml of commercil Me/MeH to 25 ml of MeH) resulting in cler solution fter bout 30 min. Stirring ws continued for nother 3 h (TLC monitoring), nd the solution ws diluted with 100 ml of MeH, nd neutrlized by stirring with owex 50 WX8, H + form, for 10 min. Filtrtion, wshing of the resin with MeH, nd in vcuo evportion of the filtrte nd wshings gve sirup, comprising n pproximte 3:2 E/Z-oximes 8h (740 mg, 87%); 1 H MR in 2 : H-3s 3.8 Hz-d t 5.10 ppm for the mjor nd 3.3 Hz-d t 4.94 for the minor isomer. The product ws directly subjected to deoximtion with cetldehyde (0.5 ml) in cetonitrile (20 ml) nd 4 ml of M HCl (5 h, rt), followed by dilution with wter (10 ml), neutrliztion with bsic resin nd in vcuo evportion to sirup. Purifiction by elution from silic gel column (2 20 cm) with 7:3 n-prh/wter nd in vcuo evportion of the product-crrying frctions left 570 mg of 9h (67%, bsed on 6c) s glss; ½Š 25 ¼ 22:3 (c 0.8, wter); 1 H MR (500 MHz, 2 ): d 4.35 (d, 1H, J 1 0,2 = 7.9 Hz, 0 H-10 ), (complex m, 6-H 2,6 0 -H 2, H-5, H-5 0 ), 3.59 nd 3.30 (two 1Hd, J 1,1 = 12.0 Hz, H-1b nd H-1), 3.50 (3H-m, H-3, H-3 0, H-4 0 ),

5 744 T. kgw, F. W. Lichtenthler / Tetrhedron: Asymmetry 22 (2011) (2H-m, H-4, H-2 0 ). 13 C MR (75.5 MHz, 2 ): d (C-1 0 ), 93.2 (C-2), 79.4 (C-4), 79.0 (C-3), 75.9 (C-5, C-5 0 ), 73.1 (C-3 0 ), 72.0 (C-1), 71.4 (C-2 0 ), 69.2 (C-4 0 ), 61.5 nd 61.2 (C-6, C-6 0 ). Anl. Clcd for C 12 H H 2 (342.30): C, 42.10; H, Found: C, 41.98; H, The MR dt reported by Agoston et l. 9 for 9h corresponded resonbly well to those described bove, yet their micronlyticl dt (found: 9 C, 39.94; H, 6.72) re too low by n intolerble 5%. Curiously, they correspond perfectly to C 12 H H 2, 9 which de fcto is dihydrte C 12 H H 2 (clcd C, 40.00; H, 6.71). References 1. Lergenmüller, M.; Kläres, U.; Lichtenthler, F. W. Crbohydr. Res. 2009, 344, effieux, G.; Bute, R.; Bute, M.-A.; Atfni, M.; Crpy, A. Phytochemistry 1987, 26, () Lichtenthler, F. W.; El Ashry, E. S. H.; Göckel, V. H. Tetrhedron Lett. 1980, 21, 1429; (b) Brehm, M.; Göckel, V. H.; Jrglis, P.; Lichtenthler, F. W. Tetrhedron: Asymmetry 2008, 19, Blir, M. G. Methods Crbohydr. Chem. 1963, 2, () Lichtenthler, F. W.; Jrglis, P. Tetrhedron Lett. 1980, 21, 1425; (b) Jrglis, P.; Lichtenthler, F. W. Angew. Chem., Int. Ed. Engl. 1982, 21, 141; Angew. Chem. Suppl. 1982, () Bute, A.; Bute, R.; effieux, G. Phytochemistry 1988, 27, 3401; (b) Tguchi, T.; Hrun, M.; kud, J. J. Biotechnol. Appl. Biochem. 1993, 18, 275; (c) Yu, S.; Kenne, M.; Pedersén, M. Biochim. Biophys. Act 1995, 1244, 1; (d) Freimund, S.; Huwig, A.; Giffhorn, F.; Köpper, S. Chem. Eur. J. 1998, 4, 2442; (e) Fujisue, M.; Yoshing, K.; Muroy, K.; Abe, J.; Hizukuri, S. J. Appl. Glycosci. 1999, 46, 439; (f) Yu, S. Zuckerindustrie (Berlin) 2004, 129, () kmur, T.; Tkhshi, A.; Kto, K. (ippon Kgku Co.) Jp. Pt , 1988, Appl. 1986; Chem. Abstr. 1988, ; (b) Lundt, I.; Stütz, A.; ekny, G.; Thiem, J.; Agoston, K.; Andressen, M. PCT Int. Appl. W ; Chem. Abstr. 2005, 144, ; (c) ekny, G.; Lundt, I.; iedermir, F.; Bichler, S.; Spreitz, J.; Sprenger, F. K.; Stütz, A. E. Crbohydr. Res. 2007, 342, Lichtenthler, F. W.; Kji, E.; Weprek, S. J. rg. Chem. 1985, 50, Agoston, K.; ékány, G.; Lundt, I. Crbohydr. Res. 2009, 344, Schmidt, R. R.; Stumpp, M. Liebigs Ann. Chem. 1983, Fiskesund, R.; Abeym, K.; Yoshing, K.; Abe, J.; Yun, Y.; Yu, S. Plnt Med. 2010, 76, Yoshing, K.; Abe, J.; Tnimoto, T.; Koizumi, K.; Hizukuri, S. Crbohydr. Res. 2003, 338, Richrd, G.; Yu, S.; Monsn, P.; Remud-Simeon, M.; Morel, S. Crbohydr. Res. 2005, 340, Jrglis, P.; Göckel, V.; Lichtenthler, F. W. Tetrhedron: Asymmetry 2009, 20, Liné, V.; Coste-Srguet, A.; Gdelle, A.; efye, J.; Perly, B.; jedini-pilrd, F. J. Chem. Soc., Perkin Trns , () Xu, X.; Tn, Q.; Hyshi, M. Synthesis 2008, 770; (b) Ro,. R.; Lerner, L. M. Crbohydr. Res. 1972, 22, 345.

Experiment 9: DETERMINATION OF WEAK ACID IONIZATION CONSTANT & PROPERTIES OF A BUFFERED SOLUTION

Experiment 9: DETERMINATION OF WEAK ACID IONIZATION CONSTANT & PROPERTIES OF A BUFFERED SOLUTION Purpose: Prt I: The cid ioniztion constnt of wek cid is to be determined, nd the cid is identified ccordingly.