bluuebunny/crossref_metadata_2025_split huggingface dataset:
Cross‐pinacol‐type coupling reactions between α,β‐unsaturated ketones and aldehydes with low‐valent metals
Authors: Takai Kazuhiko , Morita Ryotaro , Matsushita Hiroshi , Toratsu Chika 
Published: December 2002

AbstractTreatment of an α,β‐unsaturated ketone and an aldehyde with chromium(II) chloride and R3SiCl in DMF gives cross‐pinacol‐type coupling products, 1,2‐diols selectively. The anti/syn ratios of the produced 1,2‐diols are shown to depend on the reaction temperature: At lower temperatures, the anti adduct is produced selectively, but at higher temperatures, the anti/syn ratios gradually decrease. When a combination of manganese and a catalytic amount of lead are used instead of chromium(II), 1,6‐diketone, a dimer of the α,β‐unsaturated ketone, is produced selectively. Chirality 15:17–23, 2003. © 2002 Wiley‐Liss, Inc.
Asymmetric oxidation of racemic 2‐substituted 1,3‐oxathianes
Authors: Saito Bunnai , Katsuki Tsutomu 
Published: December 2002

AbstractRacemic 2‐substituted 1,3‐oxathianes were oxidized with good to high enantiomer‐differentiation by using urea hydrogen peroxide addition compound as oxidant in the presence of a catalytic amount of di‐μ‐oxo Ti(salen) complex, giving the corresponding sulfoxides diastereoselectively. Chirality 15:24–27, 2003. © 2002 Wiley‐Liss, Inc.
1,2‐Silyl‐migrative cyclization of vinylsilanes bearing an amino group
Authors: Miura Katsukiyo , Takahashi Tatsuyuki , Hondo Takeshi , Hosomi Akira 
Published: December 2002

AbstractIn the presence of an acid catalyst, α‐alkyl‐substituted (Z)‐vinylsilanes 1, bearing a tosylamino group, were smoothly cyclized to trans‐2‐alkyl‐3‐silylpiperidines 2 (1,2‐silyl‐migration products) and (2R*, 1′S*)‐2‐(1′‐silylalkyl)pyrrolidines 3. The elaboration of the reaction conditions enabled the selective preparation of each cyclized product. The acid‐catalyzed cyclization of (Z)‐vinylsilane 5, whose methylene tether is shorter than that of 1 by one carbon, formed only the 1,2‐silyl‐migration product 6 with high trans‐selectivity. These cyclizations were found to proceed in a stereospecific manner. Chirality 15:41–52, 2003. © 2002 Wiley‐Liss, Inc.
Asymmetric carbon–carbon bond‐forming reaction at the 2‐position of a piperidine skeleton
Authors: Kanda Yasuhisa , Onomura Osamu , Maki Toshihide , Matsumura Yoshihiro 
Published: December 2002

AbstractAn asymmetric carbon–carbon bond‐forming reaction at the 2‐position of a piperidine skeleton was exploited. This method consisted of a reaction between 1‐(4‐methoxybenzoyl)‐3,4‐didehydro‐2‐methoxypiperidines and dimethyl malonate catalyzed by Cu(II)‐chiral 2,2′‐isopropylidenebis(4‐phenyl‐2‐oxazoline) to afford a 2‐substituted piperidine skeleton with moderate enantioselectivity. Chirality 15:89–94, 2003. © 2002 Wiley‐Liss, Inc.
Highly diastereoselective addition of silyldihalomethyllithiums to chiral alkyl esters
Authors: Shinokubo Hiroshi , Kondo Junichi , Inoue Atsushi , Oshima Koichiro 
Published: December 2002

AbstractTreatment of benzoate, formate, or trifluoroacetate esters with silyldibromomethyllithiums provides alkyl silyl mixed acetals via the 1,3‐rearrangement of a silyl group from carbon to oxygen. A high level of asymmetric induction onto the acetal carbon is observed when chiral alkyl esters are employed. The stereochemical assignment of the silyl acetal 13j was accomplished on the basis of X‐ray crystallographic analysis. A one‐pot synthesis of a three‐component coupling product R1C(OR2)(OSiMe2‐t‐Bu)CX2E′ (X = Cl, Br) by sequential additions of an ester (R1CO2R2) and the second electrophile was achieved. Chirality 15:31–37, 2003. © 2002 Wiley‐Liss, Inc.
Interpretation of enantioresolution in nordeoxycholic acid channels based on the four‐location model
Authors: Kato Kazuaki , Aoki Yuriko , Sugahara Michihiro , Tohnai Norimitsu , Sada Kazuki , Miyata Mikiji 
Published: December 2002

AbstractNordeoxycholic acid (NDCA) forms three kinds of host frameworks, M1, M2, and M3, with channels where aliphatic alcohols (1–7) are accommodated. 13C‐NMR studies clarified that racemic alcohols 1‐ or 2–6 are enclosed in the M1‐ or M2‐type channel with lower than 15% enantiomeric excess, respectively, while 3‐methyl‐2‐pentanol (7) is done in the M3‐type with 47% ee. These inclusion phenomena can be explained due to the Difference Fourier maps of electron densities of their enantiomers in the channels. In addition, analysis of the manner of packing indicates that four locations in the channels should be fixed for the enantioresolution of the alcohols. These results support the four‐location model, which has been proposed by Mesecar et al.20 with respect to enantioresolution on protein surfaces. Chirality 15:53–59, 2003. © 2002 Wiley‐Liss, Inc.
Stereospecific substitution at α‐carbon to trifluoromethyl group: Application to optically active fluorinated amino acid syntheses
Authors: Katagiri Toshimasa , Uneyama Kenji 
Published: December 2002

AbstractThis account summarizes how we performed the intramolecular nucleophilic substitutions of the hydroxy groups at α‐position to trifluoromethyl group. The origin of the steric hindrance of the trifluoromethyl group was found to be the electrostatic repulsive force between the nucleophile and the negatively charged fluorine atoms. Chirality 15:4–9, 2003. © 2002 Wiley‐Liss, Inc.
Practical asymmetric Mukaiyama‐Michael reaction of benzalacetone derivatives catalyzed by allo‐threonine‐derived oxazaborolidinone
Authors: Wang Xiaowei , Harada Toshiro , Iwai Hiroyoshi , Oku Akira 
Published: December 2002

AbstractIn the presence of 2,6‐diisopropylphenol and t‐BuOMe (1 equiv. each), asymmetric Mukaiyama‐Michael reaction of a variety of benzalacetone derivatives 2 with silyl ketene acetal 3 is efficiently catalyzed by O‐(2‐naphthoyl)‐N‐tosyl‐(L)‐allo‐threonine‐derived B‐phenyloxazaborolidinone 1 (10 mol%) to give the corresponding adducts 5 in 60–90% ee. Chirality 15:28–30, 2003. © 2002 Wiley‐Liss, Inc.
Molecular design of DABNTf as a highly efficient resolving reagent for racemic Pd complex with Tropos biphenylphosphine (BIPHEP) ligand: Circular dichroism (CD) spectra of enantiopure BIPHEP‐Pd complex
Authors: Mikami Koichi , Yusa Yukinori , Aikawa Kohsuke , Hatano Manabu 
Published: December 2002

AbstractThe racemic Pd complexes with chirally flexible (tropos) biphenylphosphine (BIPHEP) ligands can be resolved but transformed into the enantio‐ and diastereo‐pure complex. The enantiopure metal complex of BIPHEP ligand is thus obtained through enantiomer‐selective complexation of a racemic BIPHEP‐Pd complex with enantiopure 1,1′‐binaphthyl‐2,2′‐di(triflyl)amide, DABNTf. The differential CD spectra of the enantiopure BIPHEP‐Pd complex is also reported. Chirality 15:105–107, 2003. © 2002 Wiley‐Liss, Inc.
Catalytic enantioselective allylation of ketones with novel chiral bis‐titanium(IV) catalyst
Authors: Kii Satoshi , Maruoka Keiji 
Published: December 2002

AbstractOur recently designed chiral bis‐titanium(IV) catalyst can be successfully utilized for the catalytic enantioselective allylation of ketones with tetraallyltin. The high asymmetric induction is achievable in the case of aromatic ketones. Chirality 15:68–70, 2003. © 2002 Wiley‐Liss, Inc.
Synthesis of new chiral bis(isoxazoline) ligands containing spiro[5.5]undecane skeleton
Authors: Arai Midori A. , Kuraishi Minori , Arai Takayoshi , Sasai Hiroaki 
Published: December 2002

AbstractNew chiral bis(isoxazoline) ligands bearing a spiro[5.5]undecane skeleton were designed and synthesized in five steps from diethyl malonate (3). These ligands showed a coordinating ability to Cu(II) as chiral ligands. A complex of (+)‐(M*,S*,R*)‐[5.5]‐SPRIX 2b and Cu(OTf)2 catalyzed the conjugate addition of diethyl‐zinc to 2‐cyclohexenone (8) to give (S)‐3‐ethyl‐cyclohexanone (9) in 93% yield with 54% ee. Chirality 15:101–104, 2003. © 2002 Wiley‐Liss, Inc.
Enantioselective electrochemical oxidation of enol acetates using a chiral supporting electrolyte
Authors: Maekawa Hirofumi , Itoh Kotaro , Goda Satoshi , Nishiguchi Ikuzo 
Published: December 2002

AbstractAnodic oxidation of 1‐acetoxy‐3,4‐dihydronaphthalene (1) and α‐acetoxy‐β‐alkylstyrenes (3) at –78°C in a mixed solvent of acetonitrile (CH3CN), tetrahydrofuran (THF), and acetic acid (AcOH) containing (S)‐tetraethylammonium camphorsulfonate as a chiral supporting electrolyte brought about enantioselective formation of the corresponding 2‐acetoxy‐1‐tetralones (2) and (R)‐2‐acetoxy‐1‐phenyl‐1‐alkanone (4) with maximum enantiomeric excess (ee) of 44% and 21%, respectively. Introduction of a 7‐methoxy group into 1 and increase in bulkiness of a β‐alkyl group in 3 resulted in improvement of enantioselectivity of the reactions. Chirality 15:95–100, 2003. © 2002 Wiley‐Liss, Inc.
Remote chirality transfer in nucleophilic catalysis with N‐(4‐pyridinyl)‐L‐proline derivatives
Authors: Kawabata Takeo , Stragies Roland , Fukaya Takayuki , Fuji Kaoru 
Published: December 2002

AbstractChiral nucleophilic catalysts 5–15 were prepared starting from L‐proline. Catalysts 9 and 14 promoted acylative kinetic resolution of racemic amino alcohol derivative 16 with selectivity factors of 8.1 and 11, respectively, at ambient temperature. Since chiral elements are not present in the catalytically active pyridine ring in these catalysts, chirality transfer from the remote stereogenic center to the reactive site (N‐acylpyridinium) is suggested to be responsible for the differentiation between enantiomers. Chirality 15:71–76, 2003. © 2002 Wiley‐Liss, Inc.
Asymmetric catalysis with self‐organized chiral lanthanum complexes: Practical and highly enantioselective epoxidation of α,β‐unsaturated ketones
Authors: Daikai Kazuhiro , Hayano Tetsuji , Kino Rie , Furuno Hiroshi , Kagawa Takumi , Inanaga Junji 
Published: December 2002

AbstractA highly efficient and practical method for obtaining α,β‐epoxy ketones with high optical purities was developed. The chiral lanthanum complex self‐organized in situ from lanthanum triisopropoxide, (R)‐BINOL, triarylphosphine oxide, and alkyl hydroperoxide (1:1:1:1) was found to catalyze the epoxidation of α,β‐unsaturated ketones with tert‐butyl hydroperoxide or cumene hydroperoxide at room temperature to give the corresponding epoxy ketones in high enantioselectivities (up to >99% enantiomeric excess (ee)). A remarkably high asymmetric amplification, a positive nonlinear effect, was observed in the epoxidation of chalcone, which strongly suggests the formation of a dinuclear peroxide‐involved μ‐complex as the active catalyst. Chirality 15:83–88, 2003. © 2002 Wiley‐Liss, Inc.
Kinetically controlled optical resolution of racemic norbornene aldehyde derivatives
Authors: Fujioka Hiromichi , Kotoku Naoyuki , Fujita Tetsuya , Inoguchi Ryoko , Murai Kenichi , Nagatomi Yasushi , Sawama Yoshinari , Kita Yasuyuki 
Published: December 2002

AbstractA new method for obtaining optically pure 5‐norbornene 2‐endo‐aldehyde derivatives was developed. The reaction of a diastereomeric mixture of the ene acetals 2 and 2′, derived from racemic norbornene aldehydes (±)‐1 and chiral nonracemic (S,S)‐hydrobenzoin 7, with NBS (0.5–0.6 eq.) in the presence of H2O proceeded in a kinetically controlled manner to give the optically pure hydroxy aldehydes 3 along with the intact ene acetals 2′. Both compounds 3 and 2′ were converted into the optically pure norbornene aldehydes 1 and ent‐1, respectively. This method opens the way to produce various types of 5‐norbornene 2‐endo‐aldehydes with 3‐exo‐ or 3‐endo‐substituents in optically pure forms. Chirality 15:60–67, 2003. © 2002 Wiley‐Liss, Inc.
Preparation of chiral stationary phase for HPLC based on immobilization of cellulose 3,5‐dimethylphenylcarbamate derivatives on silica gel
Authors: Kubota Takateru , Yamamoto Chiyo , Okamoto Yoshio 
Published: December 2002

AbstractThe immobilization of cellulose 3,5‐dimethylphenylcarbamate derivatives having a polymerizable vinyl group, i.e., 4‐vinylphenylcarbamate or 2‐methacyloyloxyethylcarbamate, on silica gel was examined under various conditions. The immobilization was basically conducted through the radical copolymerization of the derivatives with a vinyl monomer. Several factors, such as the vinyl monomer content and the type and amount of the vinyl group of cellulose derivatives, were varied. The introduction of a vinyl group onto the silica surface resulted in a more efficient immobilization of the cellulose phenylcarbamate derivatives on the silica gel. As the content of the vinyl group on the cellulose derivatives was reduced, the immobilization became more difficult, although the obtained phase exhibited higher chiral recognition abilities. These immobilized CSPs could be stably used with the eluent containing 10% chloroform, which cannot be used for the phase prepared by coating the derivatives on silica gel. Some racemates were better resolved on the immobilized CSP by using chloroform as a component of the eluent. Chirality 15:77–82, 2003. © 2002 Wiley‐Liss, Inc.
Stereospecific synthesis of aldoses based on the epoxide‐opening reaction with double inversion of the configuration
Authors: Hirai Atsushi , Tonooka Terumichi , Tanino Keiji , Miyashita Masaaki 
Published: December 2002

AbstractA new synthetic methodology for aldoses and aldonitols was developed in which two stereospecific epoxide‐opening reactions with double inversion of the configuration, i.e., the ring‐opening reaction of epoxy sulfides with phenylboronic acid and the stereospecific interconversion of trans‐ and cis‐epoxy sulfides, were designed as the key steps. The synthetic potential of the new methodology was exemplified by the highly stereoselective synthesis of two pentose‐derived sugars, arabitol and adonitol (ribitol). Chirality 15:108–109, 2003. © 2002 Wiley‐Liss, Inc.
Sequelae of axillary lymph node dissection in older women with stage 1 and 2 breast carcinoma
Authors: Mandelblatt Jeanne S. , Edge Stephen B. , Meropol Neal J. , Senie Ruby , Tsangaris Theodore , Grey Luther , Peterson Burt , Hwang Yi‐Ting , Weeks Jane C. 
Published: December 2002

AbstractBACKGROUNDThere are few data on the long‐term sequelae of axillary dissection among older breast carcinoma patients. We describe the impact of axillary dissection in a cohort of older women.METHODSA longitudinal cohort of 571 patients with Stage 1 and 2 breast carcinoma, 67 years and older, diagnosed between 1995 and 1997 from 29 hospitals in five regions, and followed for 2 years. Data were collected from patients and medical charts. The primary outcome was posttreatment quality of life. Generalized estimation equation longitudinal modeling was used to evaluate the outcome, controlling for baseline function, comorbidity, age, clinical status, and other factors.RESULTSSixty percent of women reported arm problems at some time in the 2 years after surgery. The cumulative risk of having arm problems 2 years posttreatment was three times higher (95% confidence interval 1.94–4.67) for women who underwent axillary surgery compared with women without axillary surgery, controlling for covariates. The effects of having axillary dissection and arthritis were multiplicative 2 years postsurgery. Arm problems were, in turn, the primary determinate of lower physical and mental functioning (P = 0.0001 and 0.04, respectively), controlling for other factors. Undergoing axillary dissection did not lessen fears about recurrence.CONCLUSIONSArm problems after axillary dissection have a consistent negative impact on quality of life, suggesting that the risks may outweigh the potential benefits in this population. Cancer 2002;95:2445–54. © 2002 American Cancer Society.DOI 10.1002/cncr.10983
Relation of regimens of combined hormone replacement therapy to lobular, ductal, and other histologic types of breast carcinoma
Authors: Daling Janet R. , Malone Kathleen E. , Doody David R. , Voigt Lynda F. , Bernstein Leslie , Coates Ralph J. , Marchbanks Polly A. , Norman Sandra A. , Weiss Linda K. , Ursin Giske , Berlin Jesse A. , Burkman Ronald T. , Deapen Dennis , Folger Suzanne G. , McDonald Jill A. , Simon Michael S. , Strom Brian L. , Wingo Phyllis A. , Spirtas Robert 
Published: December 2002

AbstractBACKGROUNDThe incidence of invasive lobular carcinoma has been increasing among postmenopausal women in some parts of the United States. Part of this may be due to changes in classification over time. However, the use of combined (estrogen and progestin) hormone replacement therapy (CHRT) also has increased during the last decade and may account in part for the increase in invasive lobular breast carcinoma.METHODSA large, multicenter case–control study of Caucasian and African‐American women who were diagnosed at age < 65 years with their first invasive breast tumor from July 1, 1994 through April 30, 1998 was conducted. In‐person interviews were conducted with 1749 postmenopausal patients, and their responses were compared with the responses of 1953 postmenopausal control women identified through random‐digit dialing who met the study criteria of being postmenopausal at the time of diagnosis. Polytomous logistic regression was used to calculate the odds ratio (OR) as an estimate of the relative risk and to compute the 95% confidence interval (95%CI) associated with the use of various regimens of hormone replacement therapy (HRT) among women diagnosed with ductal breast carcinoma, lobular (or mixed lobular and ductal) breast carcinoma, and a grouping of other histologic types of breast carcinoma.RESULTSEver use of unopposed estrogen therapy (ERT) was not associated with an increase in the risk of any histologic type of breast carcinoma. The risk of invasive lobular breast carcinoma and the risk of breast carcinoma of the grouping of other histologies increased among women currently using CHRT (OR, 2.2; 95%CI, 1.4–3.3; and OR, 1.9; 95%CI, 1.0–3.4, respectively). The risk increase was greater for the mixed lobular‐ductal type than for the pure lobular type of breast carcinoma, although the difference was not statistically significant. There was some indication that ≥ 5 years of continuous CHRT (≥ 25 days per month of progestin) was associated with a higher risk of lobular breast carcinoma (OR, 2.5; 95%CI, 1.4–4.3) compared with sequential CHRT (< 25 days per month of progestin; OR, 1.5; 95%CI, 0.8–2.6). Current use of continuous CHRT was only moderately associated with risk of ductal breast carcinoma.CONCLUSIONSPostmenopausal women who take CHRT appear to be at an increased risk of lobular breast carcinoma. Data from this study suggest that neither ERT use nor CHRT substantially increase the risk of ductal breast carcinoma among women age < 65 years. Cancer 2002;95:2455–64. Published 2002 by the American Cancer Society.DOI 10.1002/cncr.10984
Advanced age and adjuvant tamoxifen prescription in early‐stage breast carcinoma patients
Authors: Blackman Sarah B. , Lash Timothy L. , Fink Aliza K. , Ganz Patricia A. , Silliman Rebecca A. 
Published: December 2002

AbstractBACKGROUNDAdjuvant tamoxifen is recommended for all women with estrogen receptor‐positive breast carcinoma without regard for age. We investigated age‐dependent variations in adjuvant tamoxifen prescription patterns in a cohort of women 80 years of age and older.METHODSWe studied 92 women diagnosed at four U.S. sites with primary, early‐stage breast carcinoma. Each woman consented to a medical record review and participated in two telephone interviews. We compared the proportion of tamoxifen prescriptions received by women 85–92 years of age with those received by women 80–84 years of age. Relative risks (RR) and 95% confidence intervals (95% CI) were generated using generalized estimating equations. Confounding by demographic, disease, and treatment characteristics was assessed.RESULTSBefore adjustment, patients 85–92 years of age were 28% less likely to receive a tamoxifen prescription compared with patients 80–84 years of age (RR = 0.72, 95% CI 0.57–0.91). In this sample, patients not prescribed tamoxifen had substantially more comorbidity. After adjusting the crude finding for comorbidity, the RR was 0.74 (95% CI 0.58–0.93). In addition, the oldest patients and those not prescribed tamoxifen were significantly less likely to be married or have living children. After adjusting the crude finding for these two factors, the RR was 0.75 (95% CI 0.59–0.95). There was no confounding by the other demographic, disease, or treatment covariates assessed.CONCLUSIONGiven the increasing longevity of the oldest old, undertreatment with adjuvant tamoxifen may put older breast carcinoma patients at an increased risk of disease recurrence and breast carcinoma mortality. Cancer 2002;95:2465–72. © 2002 American Cancer Society.DOI 10.1002/cncr.10985
A survival–stratification model of human colorectal carcinomas with β‐catenin and p27kip1
Authors: Cheah Peh Yean , Choo Poh Heok , Yao Jocelyn , Eu Kong Weng , Seow‐Choen Francis 
Published: December 2002

AbstractBACKGROUNDThe stabilization and nuclear translocation of β‐catenin are early events in the majority of sporadic colorectal carcinomas (CRC). β‐catenin up‐regulates c‐Myc and cyclin D1, which antagonize the association of the cyclin‐dependent kinase (Cdk) inhibitor, p27kip1, with Cdk2, thus allowing cell cycle progression through G1 to S‐phase. Lack of p27 is a significant predictor of poor survival in a series of 136 CRC specimens. A combination of molecules in the same pathway may be a better prognostic factor.METHODSThe expression of β‐catenin, c‐Myc, and cyclin D1 in relation to patients' survival and clinicopathologic parameters in the same series was evaluated by immunohistochemistry.RESULTSIntense nuclear overexpression of β‐catenin, but not a lack of cell membrane or cytoplasmic expression, is a significant predictor of poor survival by both univariate (P = 0.0029) and multivariate analyses (P = 0.004, risk ratio =3.8), suggesting that β‐catenin is retained in the nucleus to function as an oncogene. None of the patients with high nuclear β‐catenin and low p27 expression survived 5 years or more whereas 65% of patients with all other combinations of the two markers survived (P < 0.0001). This combination is also a significant and independent prognostic factor (P = 0.001; risk ratio = 9.7). Overexpression of c‐Myc is associated with higher mortality rates, but the expression of cyclin D1 has no prognostic significance.CONCLUSIONSThe combined expression of β‐catenin and p27 can stratify patients into markedly different survival groups, possibly via their antagonistic effects on metastasis promotion. Cancer 2002;95:2479–86. © 2002 American Cancer Society.DOI 10.1002/cncr.10986