Carbon-13 nuclear magnetic resonance spectra of cinchona alkaloids

Moreland, Charles G.; Philip, A.; Carroll, F. Ivy

doi:10.1021/jo00930a020

Cited by 57 publications

(32 citation statements)

References 2 publications

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“…4, and the corresponding peak assignments provided in Table 2. The latter were made by analogy with reported spectra for free cinchonidine [31]; the same convention used there has been used here to label the carbon atoms. The two bottom Fig.…”

Section: Resultsmentioning

confidence: 99%

“…The differences seen between the latter two spectra attest to the success of the tethering chemistry Table 2 Assignment of 13 C NMR spectra in Fig. 4 [31] Shift d/ppm Assignment correspond to the original molecule, unreacted, whereas the other spectra all show new peaks consistent with the formation of the 3-(p-tert-butylbenzenelthio)cyclohexanone product. Close to 100% conversion was observed after 24 h of reaction at room temperature in all cases.…”

Section: Resultsmentioning

confidence: 99%

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Cinchona Alkaloids Tethered on Porous Silica as Enantioselective Heterogeneous Catalysts

2011

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Cinchonidine, a naturally occurring cinchona alkaloid, was tethered to a high-surface-area silica substrate in order to create a new solid chiral catalyst. Two synthetic routes were explored for this grafting, relying on the use of an intermediate linker and so-called ''click'' chemistry. Both routes proved viable, but the procedure where cinchonidine is first derivatized with 3-isocyanatopropyltriethoxysilane (ICPTEOS) at the alcohol position and the resulting product then anchored to the silica surface was deemed the most efficient. Bonding to the surface occurs via the formation of Si-O-Si bonds, on average two out of the three possible per cinchonidine, and takes place preferentially at silica surface sites with two geminal hydroxyl groups on the same silicon atom. Approximately 10% of the available OH surface groups are derivatized in this procedure. The resulting catalyst was successfully tested for the addition of aromatic thiols to unsaturated ketones, a reaction promoted by amines (the tertiary quinuclidine nitrogen atom in the case of cinchonidine). The activity of the supported cinchonidine proved comparable to that of the free molecule, but tethering does lead to a significant loss in enantioselectivity.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Cinchona Alkaloids Tethered on Porous Silica as Enantioselective Heterogeneous Catalysts

2011

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“…The 13C results for 9 and 10 are summarized in Table 3 along with the results for lycodine (11) and N-methyllycodine (12) which were used as model compounds to aid in the chemical shift assignments. The assignments for 9-12 were Can.…”

Section: Yh3mentioning

confidence: 99%

Carbon-13 Nuclear Magnetic Resonance Studies of Some Lycopodium Alkaloids

Nakashima¹,

Singer²,

Browne³

et al. 1975

Can. J. Chem.

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Chem. 53,1936 (1975).The natural abundance 13C magnetic resonance spectra of some Lycopodium alkaloids have been determined at both 25.15 and 22.63 MHz. By using standard techniques it has been possible to make self-consistent assignments of almost all of the resonances. The results suggest some interesting conclusions regarding the stereochemistry of some of the alkaloids and have been used to confirm the stereochemical assignment at C-12 in sauroxine and to assign the preferred conformation (axial) of the N-methyl group in the obscurines and N-methyllycodine. THOMAS T. NAKASHIMA, PETER P. SINGER, LOIS M. BROWNE et WILLIAM A. AYER. Can. J. Chem. 53,1936Chem. 53, (1975.On a determine, i 25.15 et 22.63 MHz, les spectres de resonance magnetique nucleaire du 13C en abondance naturelle de quelques alkaloides Lycopodium. Utilisant les techniques habituelles, on a pu faire des attributions cohkrentes de pratiquement toutes les resonances. Les resultats obtenus suggkrent quelques conclusions interessantes concernant la stereochimie de quelqu'uns des alkaloides et ces rCsultats ont etC utilisb pour confirmer I'attribution stereochimiqueen C-12 dans la sauroxine et pour attribuer la conformation priviligik (axiale) du groupe N-methyle des obscurines et de la N-methyllycodine.[Traduit par le journal]

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“…13,15 Sulfanyl Derivatives of Cinchona Alkaloids 2 and 5; General Procedure A solution of alkaloid 1 or 4 (1 mmol), ArSSAr (3 mmol), and Bu 3 P (585 mg, 0.713 mL, 4 mmol) in anhyd toluene (8 mL) was placed under argon in an ampoule. The sealed tube was heated at 65°C for 5 d. Thereafter, the cooled mixture was diluted with Et 2 O (5 mL) and washed with aq 5% NaOH (5 mL).…”

Section: Epi-quinidinementioning

confidence: 99%

Simple Enantiospecific Synthesis of Sulfides ofCinchonaAlkaloids

Zielińska-Błajet¹,

Kucharska²,

Skarżewski³

2006

Synthesis

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The native and epi-Cinchona alkaloids were reacted with (ArS) 2 /Bu 3 P in toluene at 65 °C to give the corresponding arylsulfanyl derivatives (15 examples, 31-75%) with complete inversion of configuration at 9-C stereogenic centers. Similar products were also obtained in the enantiospecific nucleophilic substitution of the 9-mesylates of alkaloids with sodium thiolates (4 examples, 73-84%) and no cinchona rearrangement was observed. The chiral thioethers obtained were preliminarily tested as N(sp 3 ), S-donating chiral ligands in the Pd-catalyzed allylic alkylation of dimethyl malonate with rac-1,3-diphenylprop-2-enyl acetate and gave the product with up to 78% ee.For the last two decades, Cinchona alkaloids have been regarded as powerful chiral auxiliaries and catalysts. 1 Their applications in the Sharpless asymmetric dihydroxylation 2 as well as asymmetric phase-transfer reactions and enantioselective meso-anhydride methanolysis 3 portray the most outstanding examples. Cinchona alkaloids have also been used effectively in the asymmetric reactions catalyzed by chiral nucleophiles. 4 Finally, it has recently been suggested that Cinchona alkaloids belong to a privileged catalyst class. These most valuable chiral auxiliaries are highly successful in enantioselective reactions of different types. 5On the other hand, the possibilities for the selective synthetic transformation of Cinchona alkaloids are rather limited. Essentially, excluding splitting and skeleton rearrangements, 6 their structure can be modified at the C-9 hydroxy group and at the quinuclidine nitrogen. The first type of modification has led to ethers, esters, and C-9 nitrogen derivatives. 1b Recently, much attention has been paid to the N,S-donating chiral ligands, which induce high enantioselectivity in Pd-catalyzed asymmetric allylic substitution. 7 Our interest in this field 7h,i turned our attention to the preparation of aryl sulfides of Cinchona alkaloids. To the best of our knowledge, their C-9 sulfur derivatives have not been reported as yet.The Cinchona alkaloid family consists of two pairs of diastereomers, namely, cinchonidine (CD)/cinchonine (CN) and quinine (QN)/quinidine (QD) (Figure 1). Their dihydro derivatives (DH-alkaloids) are also available. Moreover, preparation of the respective C-9-epi-configured alkaloids adds another set of compounds accessible for further elaboration. 8 We were interested in the transformation of all these secondary alcohols into a library of corresponding new sulfur compounds, and prospective catalytic chiral ligands with the nitrogen/sulfur-donating functions. In this paper we describe a simple stereospecific transformation of the native and C-9-epi-alkaloids to the respective sulfanyl derivatives. Figure 1 Cinchona alkaloidsFirstly, the native alkaloids were converted into their mesylate esters 8b in 83-95% yields. These products were hydrolyzed in the presence of (+)-tartaric acid 8 and gave the respective epi-alkaloids in 70-78% yields (Scheme 1, Table 1).

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Carbon-13 nuclear magnetic resonance spectra of cinchona alkaloids

Cited by 57 publications

References 2 publications

Cinchona Alkaloids Tethered on Porous Silica as Enantioselective Heterogeneous Catalysts

Cinchona Alkaloids Tethered on Porous Silica as Enantioselective Heterogeneous Catalysts

Carbon-13 Nuclear Magnetic Resonance Studies of Some Lycopodium Alkaloids

Simple Enantiospecific Synthesis of Sulfides ofCinchonaAlkaloids

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