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cis-p-Coumaroylagmatine (1) was isolated from Albizzia julibrissin Durazz, a nyctinastic plant, as a leaf-opening substance. The compound was quite effective for opening the plant leaves at 5×10(-6) M at night, but was not effective for other nyctinastic plants. The bioactive fraction with leaf-closing activity was also separated from the plant extract. Although the leaf-opening activity of the plant extract changed between the day and night, the content of 1 was almost constant through a 24-h day. These results suggest that the change in content of an unknown leaf-closing factor induced balance between the two leaf-movement factors through a 24-h day.

Electrochemical bromination of germacrene D 1 and geraniol 2 carrying plural olefinic bonds provided the corresponding brominated products 3–10. The bicyclic derivative 6 was preferentially produced from 1, while chemical brominations provided no clear selectivity of its product distribution. Influence of the parameters of the electrochemical reaction conditions was evaluated, aiming at improvement of regioselectivity and yields of the brominated products.

Circadian rhythmic plant leaf movement, called nyctinasty, is controlled by a time-course change in the internal concentration of the leaf-movement factor in the plant body. We report that specific binding protein (210 and 180 kDa) for a leaf-movement factor, potassium lespedezate, is contained in the plasma membrane of the plant motor cell. These proteins would be potential receptors for leaf-movement factor to control the leaf movement.

The conformation of the 11-membered ring of the lathyrane skeleton has been investigated using NMR spectra and theoretical calculations. Some other skeletons, such as jatrophane, jatrapholane, and tigliane, seem to be derived from this framework, and the conformation is important in connection with the configuration of the resultant diterpenes. The conformation of lathyrane is principally defined by the orientation of the two methyl groups; namely, the methyl groups on C1 and C6 directed above or below the ring plane. Theoretical calculations revealed that the predominant conformation is altered depending on the oxygen functional groups on the ring. As far as the bond lengths, bond angles, and dihedral angles are concerned, all calculation methods afforded reasonable results. In contrast, as regards conformational stability, only the ab initio molecular orbital method (RHF/6-31G*) predicted the most stable conformation, consistent with NOE experiments. On the other hand, the stable conformations predicted by the ab initio method (RHF/STO-3G), the semi-empirical molecular orbital method (MOPAC(PM3)), and the molecular mechanics calculations (MM3) did not necessarily agree with the conformers suggested by the NOE experiments.Key words: ab initio MO, semi-empirical MO, molecular mechanics, 11-membered ring conformation, NOE.

Albiziahexoside (1), a new hexaglycosylated saponin, was isolated from leaves of Albizzia lebbeck. Saponin 1, which is an analog of cytotoxic albiziatrioside A (2), did not show cytotoxicity. However, 1 is a potential source of 2 and related bioactive saponins for medicinal use because leaves, which can be regenerated after collection, contain 1 in substantial quantity.

Nyctinasty has been known since pre-Christian era, whereas the question ‘Why do leguminous plants sleep?’ has always puzzled scientists. This paper gives a clue to the historical mystery: by using synthetic inhibitors for nyctinasty, we found that legumes cannot survive without nyctinasty.

There are fewer weeds in the ground covered with pinecones of Japanese red pine trees (Pinus densiflora Sieb. et Zucc.) than in the ground without pinecones. When six species of seeds were cultured with Japanese red pinecones on agar, the growth of cress, lettuce and cat's eye were inhibited. Pinecones had a plant species-selective influence on their growth. Exudates of the pinecones showed high biological activity and also plant species-selective activity. Some species-selective allelopathic substances may be released from the pinecones. One of the inhibiting allelopathic substances was isolated from the exudates of the pinecones using a bioassay of cat's eye. The substance was identified as phenylacetic acid from an ESI-MS and 1H NMR spectra. It inhibited shoot and radicle elongation of cat's eye at concentrations of 30–100 p.p.m. The substance was also isolated from an agar medium after removal of the pinecones. These results suggest that pinecones may inhibit some weeds that grow around pine trees. There are many reports of the allelopathic effect of leaves, bark and roots of many plants, however, this is the first report that reveals the cone also affects the allelopathy phenomenon in Japanese red pine trees.

We developed fluorescent probes ( 1 and 2 ) based on the structure of cis-p -coumaroylagmatine ( 3 ), a leaf-opening substance of Albizzia julibrissin Durazz. These probes were effective for the leaf-opening of A. julibrissin , and specifically bind to the motor cell of this plant. Moreover, binding of the fluorescent probe was specific to the plant motor cell contained in the plants belonging to the Albizzia genus. These results showed that the binding of a probe compound with a motor cell is specific to the plant genus and suggested that the genus-specific receptor molecule for the leaf-movement factor on a motor cell would be involved in nyctinasty.

Summary The role of myrosinase (β-thioglucoside glucohydrolase, EC 3.2.3.1) in the phototropic response in radish hypocotyls was investigated. Unilateral illumination with blue light abruptly up-regulated the activity of myrosinase, which releases bioactive 4-methylthio-3-butenyl isothiocyanate (MTBI) from inactive 4-methylthio-3-butenyl glucosinolate (MTBG), in the illuminated halves of radish hypocotyls 10 min after onset of phototropic stimulation, peaking after 30 min and decreasing thereafter. The myrosinase activity in the shaded halves also increased, but was significantly lower than that in the illuminated halves. Furthermore, whether blue light illumination induces myrosinase gene expression was studied. Northern blotting analysis indicated that myrosinase mRNA levels were increased markedly in unilaterally illuminated hypocotyls, reaching maximum signal intensity within 10 min after onset of blue illumination, declining nearly to the control level thereafter. These results suggested that phototropic stimulation promotes myrosinase gene expression and myrosinase activity in the illuminated side, resulting in the conversion of inactive MTBG to active MTBI and simultaneously producing more active raphanusanins, causing a phototropic response.

Most leguminous plants close their leaves in the evening, as if to sleep, and open them early in the morning according to the circadian rhythm controlled by a biological clock. Extensive studies on nyctinastic plants led to the isolation of a variety of leaf-closing and -opening substances. And we found that the biological clock regulates the balance of concentration between leaf-opening and -closing substances in the plant body during the day.

Most leguminous plants close their leaves in the evening, as if to sleep, and open them early in the morning. This circadian rhythm is known to be controlled by the biological clock of such plants. Extensive studies on other nyctinastic plants led to the isolation of a variety of leaf-closing and leaf-opening substances. And we found that the circadian rhythmic leaf-movement of these plants is controlled by a biological clock that regulates the balance of concentration between leaf-opening and -closing substances.

Nyctinastic leaf-movement, which is folding and opening movement of the leaves according to circadian rhythm, have been widely observed in leguminous plants. Although this movement has been known since the age of Alexander the Great, the question ‘Why does leguminous plant sleep?’ has always puzzled many scientists studying nyctinasty. We have revealed that nyctinastic leaf-movement is essential for the survival of leguminous plants by inhibiting leaf-movement using synthetic leaf movement inhibitor. Leguminous plant will wither and die without nyctinasty. Our result gives an important clue for the historic mystery, ‘Why does the leguminous plant sleep?’

We isolated 4- O - β - d -glucopyranosyl- trans - p -coumarate ( 1 ), the leaf-opening substance of Sesbania exaltata Cory. The leaf-movement inhibitor, designed on the chemical mechanism of nyctinasty, could keep the leaves of S. exaltata open till the leaves withered and died.

Reactivity of the anodic oxidation of 4-methoxy-1-naphthol 1 in the presence of nucleophiles has been investigated. The reaction with electron-rich alkenic nucleophiles such as 1-methoxy-4-propenylbenzene 2 and isosafrole 3 gave a very high yield, whereas the reaction with dihydropyran 4 and dihydrofuran 5 gave a moderate yield, but with ethyl vinyl ether 6 gave a very low yield of the substituted dihydronaphthofuran derivatives 7–10 and 12 , respectively. Unexpectedly, the glycosyl derivative 11 was preferentially produced rather than naphthofuran 10 upon using 5 as a nucleophile. In addition, the dimers 15 and 16 were obtained in moderate yield without addition of nucleophile to 1 . The mechanism of the oxidation reactions including the [3+2] and [5+2] cycloaddition were discussed.

Novel and non-radioactive photoaffinity probes ( 1 and 2 ) for the bioorganic study of nyctinasty are designed and synthesized based on potassium isolespedezate ( 3 ), which induce leaf-opening against the leaf of Cassia mimosoides L. These probes bear a trifluoromethyldiazirine or diazophenyl group for photoaffinity and a biotin subunit for affinity chromatography and chemiluminescent detection. Probes ( 1 and 2 ) showed leaf-opening activity at 5×10−5 mol/L with leaves of C. mimosoides; thus, they would be an important tool for the identification of a receptor protein for 3 .

A search for growth inhibitors in rice root exudates was undertaken in order to clarify the allelopathic system in rice (Oryza sativa L.). Rice seedlings inhibited the growth of cress (Lepidium sativum L.) and lettuce (Lactuca sativa L.) seedlings when the cress and lettuce were grown with rice seedlings. The putative compound causing the inhibitory effect of rice seedlings was isolated from their culture solution, and the chemical structure of the inhibitor was determined by spectral data as momilactone B. Momilactone B inhibited the growth of cress and lettuce seedlings at concentrations greater than 3 and 30 microM, respectively. The concentration of momilactone B was 3.4 and 1.1 nmol per seedling in the culture solutions of husked and non-husked rice seedlings, respectively. These results suggest that rice seedlings may release momilactone B into the environment and the stress caused by the husk-treatment may increase the amount of momilactone B released. Thus, momilactone B may play an important role in rice allelopathy.

Anodic oxidation of 4-methoxy-1-naphthol 1 in the presence of nucleophiles provided the corresponding products 8 – 12 and the dimers 13 and 17 were also produced. The reaction mechanism of the oxidation reaction including the [3+2] cycloaddition was investigated.

The anodic oxidation of phenol derivatives generates radical and cationic species, which upon coupling with other radicals, nucleophiles, and dienophiles provide a variety of bioactive natural products. The reaction conditions are controlled by electric potentials, solvents, supporting salts, electrodes, and so on to obtain the desired products. Both single- and two-electron reactions have been studied. The application of these reactions towards the synthesis of several target molecules will be discussed here.

Potassium (2R,3R)-2,3,4-trihydroxy-2-methylbutanoate (1) was identified as a leaf-closing substance in the nyctinastic plant, Leucaena leucocephala. Compound 1 showed strong leaf-closing activity toward L. leucocephala and was not effective against other nyctinastic plants. The potassium ion was indispensable for the bioactivity of 1. Compound 1 gradually lost its bioactivity because of the exchange of the counter cation during isolation. A leaf-opening substance was also observed in the same plant.

As candidate(s) for allelopathic substance(s), two plant growthinhibitors were isolated from aqueous leachate of leaves of mesquite, whichshowa strong allelopathy, and which were identified as syringin and(–)-lariciresinol by their spectral analyses. Syringin inhibited root andshoot growth of lettuce seedlings at concentrations greater than 0.8μM, and root and shoot growth of barnyard grass seedlings atconcentrations greater than 2.7 and 26.9 μM, respectively. Onthe other hand, (–)-lariciresinol inhibited root and shoot growth oflettuce seedlings at concentrations greater than 2.8 and 0.8μM,and root and shoot growth of barnyard grass seedling at concentrations greaterthan 0.8 and 2.8 μM, respectively. The contents of syringin and(–)-lariciresinol in the rhizosphere soil of mesquite were 0.34 and 0.38μg/g soil, respectively. These results indicate that syringinand (–)-lariciresinol are allelopathic substance(s), and may play rolesinthe allelopathy of mesquite.

We synthesized fluorescence-labeled probe compounds bearing 6-((7-amino-4-methylcoumarin-3-acetyl)amino)-hexanoyl (AMCA, 1), 6-N-(7-nitrobenz-2-oxa-1, 3-diazol-4-yl)-aminohexanoyl (NBD, 2), and 6-(4-((5-dimethylaminonaphthalene-1-sulfonyl)-amino))-hexanoyl (dansyl, 3) groups as the fluorescent functionality. In these probe compounds, NBD-type probe, 2, showed leaf-opening activity at 5×10−6 M. The bioactivity of 2 is one-fifth as strong as that of the natural product, potassium isolespedezate (6). We carried out the binding experiment using 1 in a plant body. Then, it was suggested that fluorescence-labeled probe compound directly bound to a motor cell in pulvina of Cassia mimosoides. And this binding was specific to C. mimosoides. Probe compounds cannot bind plant sections of other nyctinastic plants.

Anodic oxidation of simple o -halogenated phenol derivatives has been investigated. Among the oxidation products, tricyclic ketone 9 was obtained, along with both the corresponding diaryl ethers 3 and 4 and the diaryls 5 – 8 . Additionally, the effect of the alkyl substituent on the oxidation mode was inspected: anodic oxidation of phenols carrying n -propyl or 3-hydroxylpropyl groups 10b and 10c mainly provided the dienone compounds 11 and 15 through two-electron oxidation.

We synthesized fluorescence-labeled probe compounds bearing AMCA (1), NBD (2), and dansyl (3) groups as the fluorescent functionality. In these probe compounds, NBD-type probe, 2, showed leaf-opening activity at 5×10−6 M. The bioactivity of 2 is one-fifth as strong as that of the natural product, potassium isolespedezate (6). We carried out the binding experiment using 1 in a plant body.

The spirodienones 5, 6, and 12–14 including optically active ones were synthesized by anodic oxidation of the corresponding phenol derivatives. Although the asymmetric centers included in the substrates had little effect on the diastereomeric selectivity of the cyclization, the asymmetric structure of the products led to a regioselective conversion into dihydrobenzopyrans 16, 17, and 21–26 under mild Lewis acid-promoted conditions.

From the exudate of germinating sunflower (Helianthus annuus L.) seeds was isolated a stereoisomer of diversifolide, 4, 15-dinor-3-hydroxy-1(5)-xanthene-12,8-olide (designated sundiversifolide) as determined by analysis of its IR, APCI-, ESI- and HR–MS and 13C and 1H NMR spectra. This substance inhibited shoot and root growth of cat's-eyes by about 50% at a concentration of 30 ppm. It also showed species-selective activity on the shoot and root growth of tested plants. When cat's-eyes seeds were incubated together with sunflower seeds, the cat's-eyes growth was inhibited. Furthermore, it was detected from an extract of river sand when sunflower seeds were incubated on the sand. These results indicate that sundiversifolide has an allelopathic function in sunflower plants.

The effects of the auxin-inhibiting substances raphanusanin ((3R*,6S*)-3-[methoxy (methylthio) methyl]-2-pyrrolidinethione, raphanusanin B)and benzoxazolinone (6-methoxy-2-bezoxazolinone, MBOA) on apical dominance of pea(Pisum sativum L. cv. Alaska) seedlings were studied.Application of raphanusanin B or MBOA to the apical bud, internode, or lateralbud of pea seedlings released apical dominance in either intact orindole-3-acetic acid (IAA )-treated, decapitated plants. These results suggestthat the auxin-inhibiting substances raphanusanin B and MBOA have activity inreleasing apical dominance. Conversely, the auxin transport inhibitors2,3,4-triiodobenzoic acid (TIBA) and 1-naphthylphthalamic acid (NPA) did notstimulate lateral bud growth when they were applied directly to the lateralbud,although application to the apical bud or internode released apical dominance.Therefore, the mode of action of raphanusanin B and MBOA in apical dominance isclearly different from that of auxin transport inhibitors. Raphanusanin B andMBOA may suppress the synthesis of growth-inhibiting factor(s) of the lateralbud induced by endogenous auxin transported from the apical bud or exogenouslyapplied auxin, and/or the action of the factor(s).

The amounts of two growth inhibitors in diffusates from illuminatedhalves of phototropically stimulated oat (Avena sativa L.)coleoptile tips were larger than those from shaded halves. The less polarinhibitor was isolated from diffusates from oat coleoptile tips illuminatedwithblue light, and identified as uridine from 1H NMR spectrum. Thedistribution of endogenous uridine in diffusates from the illuminated andshadedsides of coleoptile tips unilaterally exposed to blue light for 3, causing a first positive phototropic curvature, and fromdark-control tips, was determined using a physicochemical assay. The uridineconcentration was significantly higher in the diffusates from the illuminatedside than in those from the shaded side and the dark-control. Uridine inhibitedthe growth of etiolated oat coleoptile tips at concentrations of 30 and above. These results suggest that uridine plays a role inthe phototropism of oat coleoptiles.

A series of sugar-modified derivatives of oxanosine and its carbocyclic analogs were synthesized from natural oxanosine and (−)-2-azabicyclo[2.2.1]hept-5-en-3-one, respectively. Among nucleosides tested for anti-HIV activities in vitro, oxanosine 1, its 5′-monophosphate 9, and 2′-deoxyoxanosine 8 reduced the number of HIV particles in CEM cells to almost the same level as ddI.

Potassium β- d -glucopyranosyl 12-hydroxyjasmonate (1) was isolated as a leaf-closing substance of a nyctinastic plant, Albizzia julibrissin Durazz. Compound 1 was quite effective for the leaf-closing of A. julibrissin at 2×10−5 M. And 1 was also effective for leaf closure of Albizzia lebbeck, which belongs to the same plant genus as A. julibrissin, at 4×10−4 M. On the other hand, HPLC and FAB MS analysis revealed that 1 was contained in A. lebbeck. Thus, leaf-closing substance of A. lebbeck would be a chemical substance the same as or structurally related to 1.

Nyctinastic leaf-movement of the plant is controlled by a biological clock. The most difficult problem encountered in the chemical studies of nyctinasty, is the isolation of chemical signals controlling this movement. Now, we have established a good procedure for isolation of the chemicals causing leaf-movement. The separation of two inversely bioactive substances, causing leaf-closing and opening movement, by Amberlite XAD-7 chromatography was very effective. Final separation with HPLC using a combination of plural ODS columns enabled us to isolate the highly polar ieaf-closing and -opening substances of Albizzia julibrissin Durazz.

In a previous paper, the syntheses of potassium galactolespedezate ( 1 ) and potassium galactoisolespedezate ( 2 ), artificial leaf-opening substances useful for bioorganic studies of nyctinasty were reported. The fluorescent probe compounds, fluorescence-labeled galactoisolespedezate ( 3 ) and iodo-one ( 4 ), designed on the basis of 1 and 2 were prepared. Especially, compound 3 was bioactive at 5×10 −5 M, one-fiftieth as strong as the natural leaf-opening substance. This fluorescent probe would be useful for bioorganic studies of nyctinasty.

The construction of the ring system of Euphoreppinol class diterpenes was accomplished. The key step of the synthesis is a biomimetic transannular double Michael cyclization of the lathyrane skeleton. The stereochemistry of the C5 hydroxy group and the junction of the B–C ring was controlled by the conformation of the lathyrane-type precursor.

The distribution of natural growth inhibitors, the raphanusanins (isomers of 3-(methylthio)methylene-2-pyrrolidinethione) and their precursors (4-methylthio-3-butenyl glucosinolate (MTBG) and 4-methylthio-3-butenyl isothiocyanate (MTBI), between illuminated and shaded halves of radish hypocotyls during phototropic curvature was analyzed using a physicochemical assay. Phototropic stimulation rapidly decreased MTBG content, and abruptly increased contents of MTBI and raphanusanins in the illuminated halves of radish hypocotyls within 30 min after the onset of unilateral illumination. Content in the shaded halves was similar to that in dark controls. When MTBG, MTBI, and raphanusanins at endogenous levels were applied unilaterally to etiolated hypocotyls, MTBI and raphanusanins caused hypocotyls to bend but MTBG showed no activity. Blue illumination promoted myrosinase (thioglucosidase) activity, which releases MTBI from MTBG, in hypocotyls after 10 min, although enzyme activity in dark controls did not change. These results suggest that phototropic stimulation promotes myrosinase activity in the illuminated side of radish hypocotyls, releasing bioactive MTBI from inactive MTBG and simultaneously producing bioactive raphanusanins.

The leaves of Mimosa pudica L. are well known for their rapid movement when touched. Recently, we were able to isolate an excitatory substance in small quantities from this plant, which consists of three different components (potassium L-malate, magnesium trans-aconitate, and dimethylammonium salt). Many plants close their leaves in the evening, as if to sleep, and open them early in the morning (nyctinastic leaf movement). This circadian rhythm is known to be controlled by the biological clock of such plants. Extensive studies on other nyctinastic plants led to the isolation of a variety of leaf-opening substances (LOSs) and leaf-closing substances (LCSs). Based on our experiments on these bioactive substances, we found that the circadian rhythmic leaf movement of these plants is initiated by the regulated balance of LOSs and LCSs. The balance of concentration between the two leaf-movement factors (LMFs) is inversed during the day. The glycoside-type LMF is hydrolyzed with β-glucosidase, the activity of which is regulated by the biological clock. The circadian rhythm observed in the leaf movement is introduced by activation of β-glucosidase regulated by the biological clock.

In a previous paper, the syntheses of potassium galactolespedezate (1) and potassium galactoisolespedezate (2), artificial leaf-opening substances useful for bioorganic studies of nyctinasty were reported. The fluorescent probe compounds, fluorescence-labeled galactoisolespedezates (3, 10, 13), designed on the basis of 1 and 2, were prepared. In particular, compound 3 was bioactive at 5×10−5 M, one-fiftieth as strong as the natural leaf-opening substance. This fluorescent probe would be useful for bioorganic studies of nyctinasty.

Three new metabolites, anthrasteroids, have been isolated from the mycelia of a hybrid strain, KO 0231, prepared by cell fusion technique using Penicillium citreo-viride IFO 6200 and 4692. Their structures were determined based on their spectral data. Furthermore, these natural products were synthesized starting from ergosterol.

A tricyclic compound ( 1 ) that has a lathyrane-type framework was designed as a model compound of the key intermediate of some diterpenes from Euphorbiacea and Thymeleacea . Two fragments 2 and 3 were derived from commercially available methyl cyclopentanone-2-carboxylate and (+)-3-carene, respectively. These fragments were coupled by a Cr(II)–Ni(II)-mediated reaction, followed by cyclization under the same conditions to afford 1 in moderate yield.

The classical experiment of phototropic response as reported by Boysen-Jensen and Nielsen (1926), which supports the Cholodny-Went theory, was repeated in detail. In the original experiment, etiolated oat (Avena sativa L. cv. Victory) coleoptiles with mica inserted into their tip only showed a positive response when the mica was placed parallel toward the light source and not if it was inserted perpendicularly. On the contrary, we found a positive response irrespective of whether the mica was inserted parallel or perpendicularly to the light source. Damage owing to rude splitting severely reduced the response upon perpendicular insertion. These results invalidate the Boysen-Jensen and Nielsen's experiment as a support of the Cholodny-Went theory and lend support to the Bruinsma-Hasegawa theory ascribing phototropism to the local light-induced accumulation of growth inhibitors against a background of even auxin distribution, the diffusion of auxin being unaffected.

Phyllanthurinolactone (1) and phyllurine (2) have been isolated as leaf-closing and -opening substance respectively, which controls the nyctinastic movement of Phyllanthus urinaria. The HPLC analysis of the content of 1 and 2 on the plant extracts showed that the content of 1 changed through a day, while that of 2 was almost constant. Thus, the nyctinastic leaf-movement was introduced by the change in the content of 1 in the plant, which is controlled by a biological clock.

Allelochemicals were isolated from the germinating maize (zea mays L.) seeds in order to know the allelopathic constituents in the plants at the early developmental stage. Three allelochemicals were found in the acetone extract obtained from the mesocotyls and coleoptiles of the 5-day-old seedlings. By spectral analysis, they were identified as 5-chloro-6-methoxy-2-benzoxazolinone (Cl-MBOA) which is a naturally occurring new benzoxazolinone, 6-methoxy-2-benzoxazolinone (MBOA) and 2,4-dihydroxy-l,4-benzoxazin-3-one (DIBOA). At concentrations greater than 0.03 mM for Cl-MBOA and DIBOA and 0.1 mM for MBOA, respectively, were inhibited the growth of the roots of cress (Lepidium sativum L.) seedlings. Activity of a new benzoxazolinone, Cl-MBOA, was greater than that of its analogue, MBOA. These results suggest that germinating maize seeds have at least three allelochemicals which may affect the growth or germination of other plant species.

Potassium β- d -glucopyranosyl 11-hydroxyjasmonate ( 1 ) was isolated as a leaf-closing substance of a nyctinastic plant, Albizzia julibrissin Durazz. Compound 1 was quite effective for the leaf-closing of A. julibrissin at 2×10 −5 M, and was proved to be a trans -isomer of β- d -glucopyranosyl tuberonic acid previously isolated from potato as a tuber-inducing stimulus.

The enantiomerically pure synthesis of 9-[(1′ R ,2′ R ,3′ S )-bis(hydroxymethyl)thietan-1′-yl]adenine 2 , 3′-thio analog of oxetanocin A, was achieved via coupling with sulfoxide 17 and 6-chloropurine in the presence of TMSOTf and Et 3 N under the Pummerer reaction conditions.