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PubMed1977

The effects of samarium on the contractile responses of the guinea-pig taenia coli to acetylcholine, potassium, histamine and barium.

The role of calcium in supporting the phasic contractions of the isolated guinea-pig taenia coli induced by acetylcholine, potassium, histamine or barium has been studied using the lanthanid samarium (Sm3+). A carefully selected concentration of Sm3+ (6 X 10(-5)M) depressed to a same extent the phasic responses of the tissue to submaximal concentrations of the agonists used whilst maximum responses to histamine and barium were unaffected. Calcium and barium-induced responses of the depolarized taenia coli were not inhibited by 6 X 10(-5)M Sm3+. The rate of loss of responsiveness of the depolarized tissue to acetylcholine was increased, that to histamine was not altered while that to barium was decreased by 6 X 10(-5)M Sm3+. These findings support the concept that phasic responses of the guinea-pig taenia coli to submaximal concentrations of the agonists used are dependent on a Sm3+-sensitive calcium store(s) probably located at the cell membrane. However, maximum responses to histamine and barium seem to be supported, at least partially, by a Sm3+-insensitive depot(s) probably located at cytoplasmic compartments.

Acetylcholine↗
PubMed1993

Samarium-153-EDTMP biodistribution and dosimetry estimation.

Fifty-two patients were treated with single doses of 153Sm-EDTMP in a Phase I escalating dose protocol for palliation of bone pain from metastatic prostate carcinoma. Samarium-153 (T1/2 46.3 hr), maximum beta-particle energies 810 keV (20%), 710 keV (30%), 640 keV (50%), gamma photon 103 keV (28%), was complexed to the tetraphosphonate chelate, EDTMP. Five groups of patients were treated at doses of 1.0, 1.5, 2.0, 2.5, and 3.0 mCi/kg to evaluate toxicity from treatment. Patients were screened prior to treatment and followed after treatment with 99mTc-MDP bone scans. Biodistribution data on this group of patients were acquired and showed rapid uptake of 153Sm-EDTMP into bone with complete clearance of nonskeletal radiotoxicity by 6-8 hr. Also included are complete sets of dosimetry estimations on an additional seven patients who received 0.5 mCi/kg 153Sm-EDTMP Ca++ as part of a multiple dose therapy trial. Estimated radiation absorbed doses to bone surfaces averaged 25,000 mrad/mCi (6686 Gy/MBq), and urinary bladder doses averaged 3600 mrad/mCi (964 Gy/MBq).

Bone Neoplasms↗
PubMed1995

Samarium-153-particulate hydroxyapatite radiation synovectomy: biodistribution data for chronic knee synovitis.

UNLABELLED: Biodistribution data for the radiation synovectomy agent samarium-153-particulate hydroxyapatite (153Sm-PHYP) are reported. METHODS: Mean extra-articular activity accumulation calculated from serial whole-body scans in 13 patients treated for chronic knee synovitis was 0.74% of injected activity (range 0%-3%). RESULTS: In four patients (31%), activity was noted in the lung (mean 0.68% of injected activity). In six patients (46%), 0.29% of injected activity accumulated in the regional lymph nodes and in three patients (23%), 0.62% of injected dose accumulated in the liver. Absorbed dose estimates were lung: 14 mGy, regional lymph nodes; 50 mGy, liver; 4 mGy. SPECT demonstrated good distribution of 153Sm-PHYP throughout the anterior knee compartments, although distribution to the posterior compartment was variable. CONCLUSION: Distribution is dependent on adequate knee flexion immediately following injection and may be influenced by the size range of labeled particles. Favorable biodistribution data suggest that 153Sm-PHYP is a potentially useful radiation synovectomy agent.

Adult↗
PubMed1993

Samarium-153-EDTMP in bone metastases of hormone refractory prostate carcinoma: a phase I/II trial.

Samarium-153-ethylenediaminetetramethylene phosphoric acid (EDTMP), a bone-seeking radiopharmaceutical, was given to prostate cancer patients in a dose escalation protocol for pain palliation to determine the maximally tolerated dose. Fifty-two patients with hormone refractory prostate cancer with bony metastases were treated with doses beginning at 0.5 mCi/kg (18.5 MBq/kg), escalating in 0.5-mCi (18.5 MBq) increments to 3.0 mCi/kg (111 MBq/kg). Pain response after treatment was assessed as well as hematologic and serum chemistry parameters. Pain palliation with a mean duration of 2.6 mo was present in 74% of the patients. Toxicity was exclusively hematologic at the highest dose levels. No infectious or bleeding complications occurred, with 45 of the 52 (86%) patients demonstrating complete hematologic recovery. Patients receiving higher doses had significantly greater reductions in serum prostate specific antigen and serum prostatic acid phosphatase levels. The patients receiving greater doses also showed a trend toward improved survival.

Aged↗
PubMed1997

[Influence on extratumoral organ activities of tumor-affinity samarium-153 preparations].

AIM: Possibilities to exercise an influence on the biodistribution of a tumor-affine 153Sm-preparation, samarium-153-nitrilotriacetate (NTA), were tested. METHODS: Animals experiments on tumor-bearing mice after additional application of EDTMP (ethylenediamine tetramethylene phosphonate) for the reduction of extratumorale liver-radioactivity and yttrium chloride for the reduction of unwanted underground radioactivity in bone were carried out. Furthermore, the combination of both measurements was tested. RESULTS: The biodistribution of 153Sm-NTA showed a rather low tumor-radioactivity of app. 0.72%/g. The additional EDTMP-application caused a dose-dependent decrease of the underground-radioactivity in liver especially if given 2 h in advance or simultaneously. The additional application of the stable yttrium salt reduced the bone radioactivity on simultaneous increase of liver- and spleen-radioactivity and practically unchanged tumor-radioactivity. The combined use of EDTMP together with the bone-affine metal salt led to a reduction of liver radioactivity on simultaneous reduction of bone radioactivity. CONCLUSIONS: The background radioactivity can be reduced on unchanged tumor-radioactivity by combined Na-EDTMP/YCl3-application. The present results do not allow a therapeutic exploitation because of the low tumor accumulation.

Animals↗
PubMed1998

Quantifying the radiation dosage to individual skeletal lesions treated with samarium-153-EDTMP.

UNLABELLED: Samarium-153ethylenediaminetetramethylenephosphonate (EDTMP) is used in the treatment of painful skeletal lesions. This study attempted to quantify the radiation dosage to individual lesions on both the macroscopic and microscopic level. METHODS: A gamma camera-based quantification technique was adapted and refined for 153Sm. The accuracy of the technique was determined by using a realistic phantom. The activity and volume of lesions as well as normal bone were determined and used to estimate the radiation dosages to these regions. Two patients died of unrelated causes shortly after receiving 153Sm-EDTMP. This made it possible to compare the gamma camera results with direct measurements. It also allowed for autoradiographic examination of the lesions. Finally, the microscopic radiation dosages were estimated. RESULTS: The phantom study indicated that the quantification technique was off, on average, by 4.1% (s.d. = 8.1%). The absolute activity concentration of trabecular bone was found to be approximately 0.22 MBq/g, and that of cortical bone was found to be approximately 0.1 MBq/g, regardless of the dosage administered. The corresponding concentrations for lesions were between 3 and 7 times higher than that of normal bone, with no apparent ceiling. From these results, the macroscopic radiation dosage could be estimated. The dosage to normal bone varied between 0.9 and 3.9 cGy x kg/MBq, and that of the lesions varied between 5.2 and 27.1 cGy x kg/MBq. The autopsy results confirmed that the gamma camera technique was accurate. The autoradiography showed clearly that the activity was associated with the surface of the bone. From these findings, the microscopic radiation dosage distribution was estimated for cortical and trabecular bone as well as osteoblastic lesions. The variation in the microscopic dosage compared to the macroscopic dosage was quite large. Microscopic dosages, when compared to the macroscopic dosages, were as high as 965% and as low as 14.9%. CONCLUSION: The techniques used have been proven to be accurate. The activity in normal bone may be at a ceiling value for all the administered doses, which could explain the small variation. This is not true for the lesions. The large variation in dosages on a microscopic scale, combined with the ceiling in normal bone, may explain the lower than expected toxicity and relatively quick relapse of the patients.

Autoradiography↗
PubMed2001

Synthesis of (E)-alpha,beta-unsaturated amides with high selectivity by using samarium diiodide.

Stereoselective beta-elimination of 2-chloro-3-hydroxyamides 1 is achieved by using samarium diiodide to yield alpha,beta-unsaturated amides 2, in which the C=C bond is di- tri-, or tetrasubstituted. The starting compounds 1 are easily prepared by reaction of the corresponding lithium enolates of alpha-chloroamides with aldehydes or ketones at - 78 degrees C. The influence of the reaction conditions and the structure of the starting compounds on the stereoselectivity of the beta-elimination reaction is also discussed.

Journal Article↗
PubMed2002

Synthesis of different deuterated carboxylic acids from unsaturated acids promoted by samarium diiodide and D2O.

An easy, and rapid reduction of the Cdbond;C bond of alpha,beta-unsaturated acids by means of samarium diiodide in the presence of D(2)O provides an efficient method for synthesizing 2,3-dideuterio acids. Starting from alka-2,4-dienoic acids, (E)-alpha,delta-dideuterio-betagamma-unsaturated acids are obtained, the new Cdbond;C bond being generated with complete diastereoselectivity. When H(2)O is used instead of D(2)O, saturated carboxylic acids and (E)-beta,gamma-unsaturated acids are isolated. A mechanism to explain each synthesis has been proposed.

Journal Article↗
PubMed2003

Progressive studies on the novel samarium-catalyzed diastereoselective tandem semipinacol rearrangement/Tishchenko reduction of secondary alpha-hydroxy epoxides.

A novel and highly diastereoselective samarium-catalyzed tandem rearrangement/reduction of secondary alpha-hydroxy epoxides, which involves a C1 to C3 carbon migration rearrangement and a very interesting hetero-Tishchenko reduction of the intermediate aldehyde and the reductant aldehyde, has been reported. This reaction could be developed to provide a facile and stereoselective construction of 2-quarternary 1,3-diol units with an hydroxymethyl moiety attached to the diastereogenic quaternary carbon center. Detailed investigations have been carried out concerning the screening of the aldehydes as a reductant, the optimization of reaction conditions, and the substrate scope of this tandem reaction. A catalytic cycle for this reaction, the electronic and steric effects of the reductant aldehydes, and the mechanism for the acyl migration of 1,3-diol monoesters are proposed.

Journal Article↗
PubMed2003

Addition reaction of vinylic reagents, derived from alpha-chloroenones, to carbonyl compounds promoted by samarium diiodide.

A new samarium diiodide-promoted addition reaction of vinylsamarium reagents, derived from (Z)-alpha-chloro-alpha,beta-unsaturated phenones 1, to both ketones (in THF) and aldehydes (in acetonitrile) led to (Z)-2-(1-hydroxyalkyl)-2,3-unsaturated ketones in good yield. These transformations took place with total or very high inversion of the stereochemistry of the C-C double bond of the starting chloroenone, producing the Z diastereoisomer. A new methodology to prepare SmI(2) in acetonitrile by sonic treatment of 1,2-diiodoethane with Sm powder is also described. A mechanism to explain this transformation is proposed.

Journal Article↗
PubMed2007

Unprecedented polymerization of trimethylene carbonate initiated by a samarium borohydride complex: mechanistic insights and copolymerization with epsilon-caprolactone.

Poly(trimethylene carbonate) (PTMC) was synthesized through ring-opening polymerization by using a rare-earth borohydride initiator, [Sm(BH(4))(3)(thf)(3)]. This initiator shows a high activity to give high-molar-mass PTMCs with molar-mass distributions ranging from 1.2 to 1.4, and with a regular structure void of ether linkages. The polymers were characterized by (1)H and (13)C NMR spectroscopy, (1)H-(1)H COSY, (1)H-(13)C HMQC NMR spectroscopy, size-exclusion chromatography (SEC), viscosimetry, and MALDI-TOF MS analyses. A coordination-insertion mechanism was established based on detailed NMR characterizations, especially of the polymer chain end-functions. The monomer initially coordinates the samarium to give [Sm(BH(4))(3)(tmc)(3)], 1. The monomer then opens up through cleavage of the cyclic ester oxygen--acyl bond and inserts into the Sm--HBH(3) bond resulting in an alkoxide complex, [Sm{O(CH(2))(3)OC(O)HBH(3)}(3)], 2, or [Sm{O(CH(2))(3)OC(O)H}(3)], 2', which then propagates the polymerization of TMC to give the active polymer [Sm({O(CH(2))(3)OC(O)}(n)O(CH(2))(3)OC(O)HBH(3))(3)], 3 or [Sm(O(CH(2))(3)OC(O){O(CH(2))(3)OC(O)}(n)O(CH(2))(3)OC(O)H)(3)], 3'. Finally, acidic hydrolysis of 3 or 3' gives HO(CH(2))(3)OC(O)[O(CH(2))(3)OC(O)](n)O(CH(2))(3)OC(O)H, 4. This novel alpha-hydroxy,omega-formatetelechelic PTMC represents the first example of a formate-terminated polycarbonate. TMC and epsilon-caprolactone (CL) were copolymerized to afford both random PTMC-co-PCL and block PTMC-b-PCL copolymers that were characterized by (1)H NMR spectroscopy, SEC, and differential scanning calorimetry (DSC). The structure of the block copolymers depends on the order of addition of monomers: if CL is introduced first, dihydroxytelechelic HO-PTMC-b-PCL-OH polymers are formed, whereas introduction of TMC first or simultaneous addition of comonomers leads to hydroxyformatetelechelic HC(O)O-PTMC-b-PCL-OH analogues.

Journal Article↗
PubMed2003

Donor-functionalized lanthanide terphenyl complexes: Synthesis and structural characterization of 2,6-di(o-anisol)phenyl compounds of ytterbium, yttrium, and samarium.

The syntheses and molecular structures of a number of 2,6-di(o-anisol)phenyl ([double bond]Danip-) -based bis(amide) and bis(alkoxide) compounds of ytterbium, yttrium, and samarium are reported. Additionally, NMR spectroscopic data are reported for the analogous diamagnetic yttrium compounds. Salt metathesis reaction of equimolar amounts of DanipLi and YbCl(3) in tetrahydrofuran at room temperature followed by addition of 2 equiv of KN(SiMe(3))(2) or KN(SiHMe(2))(2) produces DanipYb[N(SiMe(3))(2)](2) (1) and DanipYb[N(SiHMe(2))(2)](2) (2), respectively. The analogous reaction using SmCl(3) and KN(SiHMe(2))(2) produces DanipSm[N(SiHMe(2))(2)](2) (3). Reaction of DanipLi and YbCl(3) in tetrahydrofuran at room temperature followed by addition of 2 equiv of KO(2,6-diisopropylphenyl) produces DanipYb[O(2,6-diisopropylphenyl)](2) (4). Our attempts to also prepare the yttrium analogue of complex 4 yielded single-crystalline material of the tetrahydrofuran adduct DanipY(THF)[O(2,6-diisopropylphenyl)](2) (5). The molecular structures of the complexes 1-4 feature five-coordinate metal atoms and coordination polyhedra which can be described as distorted square-pyramidal rather than trigonal-bipyramidal, with the ipso carbon atom occupying the apical position. On the other hand, the molecular structure of the tetrahydrofuran-solvated yttrium Danip arylalkoxide compound 5 features a six-coordinate metal atom in a distorted trigonal-prismatic coordination environment. In all cases the Danip ligand system adopts the chiral (racemic) d,l form.

Journal Article↗
PubMed2003

Terphenyl cyclooctatetraenyl compounds of samarium.

The syntheses and molecular structures of a number of terphenyl-based compounds of the lanthanide element samarium are reported. Reaction of 2 equiv of DppLi (Dpp = 2,6-diphenylphenyl) with 1 equiv of SmCl(3) in tetrahydrofuran at room temperature yields (Dpp)(2)SmCl(micro-Cl)Li(THF)(3) (1). The one-pot reaction of 1 equiv of K(2)COT (COT(2)(-) = cyclooctatetraenyl dianion) with 1 equiv SmCl(3) in tetrahydrofuran at room temperature followed by addition of 1 equiv of terphenyllithium salt DppLi, DmpLi (Dmp = 2,6-dimesitylphenyl), or DanipLi (Danip = 2,6-di(o-anisol)phenyl) produces DppSmCOT(micro-Cl)Li(THF)(3) (2), DmpSm(THF)COT (3), and DanipSm(THF)COT (4), respectively. In the case of the Danip-based compound 4 the order of addition of reagents can be reversed producing the same compound, however, in considerably lower yield. Compound 2 can also be prepared by reaction of 1 with 1 equiv of K(2)COT in tetrahydrofuran. The molecular structure of the bis(terphenyl) compound 1 exhibits a formally four-coordinate metal atom. The molecular structures of the terphenyl COT compounds 2-4 feature monomeric complexes which are obtained either as a lithium chloride adduct (2) or as tetrahydrofuran adducts (3, 4). In 4 the Danip ligand adopts the meso form.

Journal Article↗
PubMed2004

Molten flux synthesis of an analogous series of layered alkali samarium selenogermanate compounds.

In this work, we used the molten chalcogenide flux synthetic method to form an analogous series of alkali samarium selenogermanates, with the general formula ASmGeSe(4) (A = K, Rb, Cs). Using a constant reactant stoichiometry, we relate the monoclinic KLaGeSe(4) structure type to the orthorhombic CsSmGeS(4) structure type. KSmGeSe(4) [in space group P2(1) with cell parameters a = 6.774(1) A, b = 6.994(1) A, c = 8.960(2) A, beta = 108.225(3) degrees, and V = 403.2(1) A(3) (Z = 2)], RbSmGeSe(4) [in space group P2(1)2(1)2(1) with cell parameters a = 6.7347(8) A, b = 7.0185(9) A, c = 17.723(2) A, and V = 837.7(2) A(3) (Z = 4)], and CsSmGeSe(4) [in space group P2(1)2(1)2(1) with cell parameters a = 6.707(2) A, b = 7.067(2) A, c = 18.334(6) A, and V = 869.1(5) A(3) (Z = 4)] were formed under identical synthetic conditions by changing the identity of the alkali ion from K to Rb or Cs, respectively. Additionally, with the substitution of sodium into the reaction, a triclinic structure with the approximate formula NaSmGeSe(4) was found with the cell parameters a = 6.897(2) A, b = 9.919(2) A, c = 11.183(2) A, alpha = 84.067(4) degrees, beta = 88.105(4) degrees, gamma = 73.999(4) degrees, and V = 731.5(3) A(3). In addition to single-crystal diffraction, Raman and diffuse reflectance UV-visible spectroscopic measurements have been used to characterize these compounds.

Journal Article↗
PubMed2006

Mechanistic evidence for intermolecular radical carbonyl additions promoted by samarium diiodide.

In this work, mechanistic studies were performed to understand the SmI2/H2O-mediated coupling of N-acyl oxazolidinones with acrylates and acrylamides, providing gamma-keto esters and amides, respectively. Our results provide experimental evidence that C-C bond formation via intermolecular radical addition reactions to carbonyl substrates can be promoted by samarium diiodide. Coupling reactions with N-cyclopropylcarbonyl-2-oxazolidinone suggest the alpha,beta-unsaturated esters/amides are reduced by the low-valent lanthanide reagent and not the N-acyl oxazolidinones, as originially proposed (J. Am. Chem. Soc. 2005, 127, 6544). Rate measurements support the preferred reduction of an acrylate or acrylamide by SmI2/H2O in the presence of an N-acyl oxazolidinone. In the absence of the N-acyl oxazolidinone, SmI2/H2O promotes dimerization of the acrylates, whereas the C=C bond of the acrylamides is reduced. In addition, coupling of the Pfp ester of Cbz-protected phenylalanine with an acrylamide leads only to reduction of the acrylamide and recovered ester, whereas the same coupling with the N-acyl oxazolidinone derivative provides the gamma-keto amides. These results imply that a pathway involving nucleophilic acyl substitution cannot take place and that a radical mechanism must be invoked to explain the C-C bond formation. We propose that the acrylate/acrylamide is reduced to a conjugated ketyl radical that adds to the exocyclic carbonyl group of the N-acyl oxazolidinone, activated through bidentate coordination to a lanthanide ion.

Journal Article↗