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PubMed2001

Stereoselective synthesis of delta-lactones from 5-oxoalkanals via one-pot sequential acetalization, Tishchenko reaction, and lactonization by cooperative catalysis of samarium Ion and mercaptan.

By the synergistic catalysis of samarium ion and mercaptan, a series of 5-oxoalkanals was converted to (substituted) delta-lactones in efficient and stereoselective manners. This one-pot procedure comprises a sequence of acetalization, Tishchenko reaction and lactonization. The deliberative use of mercaptan, by comparison with alcohol, is advantageous to facilitate the catalytic cycle. The reaction mechanism and stereochemistry are proposed and supported by some experimental evidence. Such samarium ion/mercaptan cocatalyzed reactions show the feature of remote control, which is applicable to the asymmetric synthesis of optically active delta-lactones. This study also demonstrates the synthesis of two insect pheromones, (2S,5R)-2-methylhexanolide and (R)-hexadecanolide, as examples of a new protocol for asymmetric reduction of long-chain aliphatic ketones.

Acetylation↗
PubMed2002

A highly stereoselective samarium diiodide-promoted aldol reaction with 1'-phenylseleno-2'-keto nucleosides. Synthesis of 1'alpha-branched uridine derivatives.

Since 1'-branched nucleosides are biologically important targets in medicinal chemistry, more efficient methods for preparing them are required. The 1'alpha-branched uridine derivatives were successfully synthesized via a samarium diiodide (SmI(2))-promoted aldol reaction. Treatment of the 1'alpha-phenylseleno-2'-ketouridine derivative 6, readily prepared from uridine, with SmI(2) at -78 degrees C in THF reductively cleaved the anomeric Se-C bond to generate the corresponding samarium enolate, which was highly stereoselectively condensed with aldehydes, such as PhCHO, MeCHO, i-PrCHO, or (CH(2)O)(n)(), to give the corresponding 1'alpha-1' 'S-branched products 12a-d. This is the first time an enolate has been generated by reductively cleaving a C-Se bond. The highly selective stereochemical results suggest that the aldol reaction proceeds via a chelation-controlled transition state. When an excess of aldehyde was used and the reaction mixture was gradually warmed, the tandem aldol-Tishchenko reaction proceeded to give the "arabino-type" nucleosides 14a-c, having a 2'-"up" hydroxyl and 1'alpha-1' 'S-branched chain. 1'alpha-Hydroxymethyluridine (21), which is the uracil version of the antitumor antibiotic angustmycin C, was synthesized from the aldol reaction product 10.

Aldehydes↗
PubMed2003

The remarkable effect of cosolvent on a samarium(II)-mediated 4-exo-trig cyclization: further synthetic studies on pestalotiopsin A.

A samarium(II)-mediated 4-exo-trig cyclization in which a remote stereocenter serves to control the facial selectivity of the cyclization is described. The apparent coordination of a tert-butyldimethylsilyl ether to the samarium center appears to give rise to the selectivity. The remarkable effect of the cosolvent, 2,2,2-trifluoroethanol, on the cyclization of this substrate, is also discussed. A stereoselective synthesis of the general class of gamma,delta-unsaturated aldehyde cyclization substrate is reported, and the utility of the cyclization is demonstrated in an approach to the fully functionalized core of pestalotiopsin A.

Cyclization↗
PubMed2005

Synthesis and theoretical analysis of samarium nanoparticles: perspectives in nuclear medicine.

The use of lanthanides as radionuclides in nuclear medicine is well-known, because they can be used for detecting and treating cancerous tumors. Due to the fact that the doses are directly related to the number of unstable atoms involved, the possibility of obtaining controlled-size lanthanide nanoparticles opens a wide scope for their application in nuclear medicine. In this work, we report the synthesis of anew samarium nanoparticle by using the bioreduction method, where the pH conditions play an important role in the size control of the produced clusters. The nanoparticles were characterized by using an transmission electron microscope, in addition to the use of a quantum mechanical method to relate the atomic and electronic structures to the chemical selectivity, which allows us to predict a direct coordination between the DTPA-bis-biotin molecules with the samarium nanoparticles larger than 55 atoms. This work involves experimental and theoretical methods to propose a totally new application for nanotechnology in nuclear medicine.

Biotin↗
PubMed1999

Facile synthesis of substituted phenanthroline ligands by samarium-promoted coupling of phenanthroline with ketones.

[formula: see text] 1,10-Phenanthroline undergoes coupling with ketones promoted by samarium diiodide to produce 2-(1-hydroxyalkyl)-1,10-phenanthrolines. O-Methylation of these derivatives provides the corresponding 2-(1-methoxyalkyl)phenanthrolines. Demethoxylation with samarium diiodide then affords 2-alkylphenanthrolines. This process may be repeated to obtain 2,9-disubstituted phenanthrolines. A variety of new, substituted phenanthrolines are thus obtained. These compounds have numerous potential applications as ligands in metal-promoted reactions, including asymmetric catalysis.

Ketones↗
PubMed2003

Application of samarium diiodide (SmI2)-induced reduction of gamma-acetoxy-alpha,beta-enoates with alpha-specific kinetic electrophilic trapping for the synthesis of amino acid derivatives.

Gamma-acetoxy-alpha,beta-enoates were easily reduced by samarium diiodide (SmI2) in THF to generate samarium dienolates which were kinetically trapped with ease at their alpha-positions by electrophiles (proton, aldehydes or ketones) to yield (E)-alkene dipeptide isosteres or gamma-amino acid derivatives in high chemical yields.

Acetates↗
PubMed2004

Beta-elimination reactions by using samarium diiodide.

The development of methodologies for the formation of carbon-carbon double bonds could be considered one of the most important challenges in organic synthesis. To this end, beta-elimination reactions in 1,2-difunctionalised substrates have been one of the most important means of generating C=C bonds. This review is intended to highlight the use of SmI2 in beta-elimination procedures, such that the organization of this revision highlights conventional beta-elimination processes which are promoted by samarium diiodide. The synthetic applications of SmI2 will be covered, and 1,2-elimination reactions which are involved in sequential reactions promoted by samarium diiodide, will also be illustrated. These methodologies along with the more recent developments in the area are discussed in this tutorial review.

Alkenes↗
PubMed2005

Evaluation of a new linker system cleaved using samarium(II) iodide. Application in the solid phase synthesis of carbonyl compounds.

A new linker design for solid phase synthesis has been developed that is cleaved under mild, neutral conditions using samarium(II) iodide. The feasibility of the linker approach has been illustrated in the solid phase synthesis of ketones and amides using an oxygen linker. Insights into the mechanism of the samarium(II) iodide cleavage reaction are described and the potential of a sequential cleavage carbon-carbon bond forming process is assessed.

Iodides↗
PubMed2003

Samarium and manganese-doped lead titanate ceramic fiber/epoxy 1-3 composite for high-frequency transducer application.

Samarium- (Sm) and manganese- (Mn) doped lead titanate ceramic fibers with a diameter of 35 microm were prepared using a sol-gel method. The X-ray diffraction pattern shows that the fibers have a pure perovskite structure. The 1-3 composite disks with a thickness of 31-41 microm and with ceramic volume fraction of approximately 0.68 have been prepared using the samarium and manganese doped lead titanate (PSmT) fibers. The resonance characteristics of the poled composite disks were measured. A focused transducer was fabricated using a concave 1-3 composite disk with nonuniform thickness in order to enhance its bandwidth. The insertion loss (IL), pulse-echo response and frequency spectrum of the composite transducer were measured. The center frequency of the transducer was approximately 31 MHz with a -3 dB bandwidth of approximately 123% and a low IL of 29.3 dB.

Ceramics↗
PubMedDate not supplied

Samarium 153-labeled hydroxyapatite microspheres for radiation synovectomy in the horse: a study of the biokinetics, dosimetry, clinical, and morphologic response in normal metacarpophalangeal and metatarsophalangeal joints.

OBJECTIVE: To determine the effects of Samarium-153 bound to hydroxyapatite microspheres (153SmM) when injected into the metacarpophalangeal and metatarsophalangeal joints of horses. STUDY DESIGN: - Horses were injected with 153SmM in metacarpophalangeal and metatarsophalangeal joints with the diagonal contralateral joints used as untreated controls. ANIMALS OR SAMPLE POPULATION: Twelve adult horses without pre-existing disease involving the metacarpo/metatarsophalangeal joints. METHODS: Horses were divided into three groups: high-dose Samarium-153 (12.5 to 17.0 millicurie [mCi]), intermediate dose (6.5 to 12.0 mCi), and low dose (3.5 to 6.0 mCi). Horses were examined daily for 7 days postinjection for clinical abnormalities, lameness, and surface and systemic radiation levels. One horse from each group was euthanatized at 14, 30, and 60 days postinjection and the effects of the 153SmM examined microscopically in the cartilage and synovial membrane. RESULTS: Intraarticular(153)SmM caused inflammation characterized by lameness, effusion, and regional edema for 48 to 72 hours. Minimal levels of active 153SmM were identified in the blood or urine and were well below the maximal tolerance of 1 mCi. Microscopically the radiation caused no effects on the articular cartilage. The synovectomy created was good but not ideal in that some areas did have necrosis into the subintimal regions and a few islands of intact intimal cells persisted. CONCLUSIONS: The use of 153SmM is an effective means of targeting the synovial intimal cells with minimal extrasynovial leakage of radiation. CLINICAL RELEVANCE: The metacarpophalangeal and metatarsophalangeal joints of the horse can be safely treated with 153SmM without damage to the cartilage or significant extracapsular leakage.

Animals↗
PubMed2005

Gemcitabine radiosensitization after high-dose samarium for osteoblastic osteosarcoma.

Osteoblastic metastases and osteosarcoma can avidly concentrate bone-seeking radiopharmaceuticals. We sought to increase effectiveness of high-dose (153)Samarium ethylenediaminetetramethylenephosphonate (153Sm-EDTMP, Quadramet) on osteosarcomas using a radiosensitizer, gemcitabine. Fourteen patients with osteoblastic lesions were treated with 30 mCi/kg 153Sm-EDTMP. Gemcitabine was administered 1 day after samarium infusion. Residual total body radioactivity was within the safe range of <3.6 mCi on day +14 (1.1 +/- 0.4 mCi; range, 0.67-1.8 mCi). All patients received autologous stem cell reinfusion 2 weeks after 153Sm to correct expected grade 4 hematopoietic toxicity. Peripheral blood progenitor cells were infused in 11 patients; three patients had marrow infused. Blood count recovery was uneventful after peripheral blood progenitor cells in 11 of 11 patients. Toxicity from a single infusion of gemcitabine (1,500 mg/m2) in combination with 153Sm-EDTMP was minimal (pancytopenia). However, toxicity from a daily gemcitabine regimen (250 mg/m2/d x 4-5 days) was excessive (grade 3 mucositis) in one of two patients. There were no reported episodes of hemorrhagic cystitis (hematuria) or nephrotoxicity. At the 6- to 8-week follow-up, there were six partial remissions, two mixed responses, and six patients with progressive disease. In the 12 patients followed >1 year, there have been no durable responses. Thus, although high-dose 153Sm-EDTMP + gemcitabine has moderate palliative activity (improved pain; radiologic responses) in this poor-risk population, additional measures of local and systemic control are required for durable control of relapsed osteosarcoma with osteoblastic lesions. The strategy of radioactive drug binding to a target followed by a radiosensitizer may provide synergy and improved response rate.

Adolescent↗
PubMed2006

Samarium for osteoblastic bone metastases and osteosarcoma.

Samarium-153 lexidronam (153Sm-EDTMP) is FDA approved for painful osteoblastic bone metastases that image on bone scan. 153Sm-EDTMP decay has a therapeutic beta-emission and a gamma-photon for bone scan imaging. Monitoring of osteosarcoma radiation treatment effectiveness was performed with bone, CT, MRI and PET/CT fusion imaging. Bone scan and PET/CT improved in 5 out of 9 and 16 out of 18 osteosarcoma sites, respectively. 153Sm-EDTMP targets multiple sites of disease, with a single administration. Side effects of 153Sm-EDTMP (0.5-2.5 mCi/kg) have been minimal and include transient thrombocytopenia and neutropenia. 153Sm-EDTMP can be combined with radiation therapy, bisphosphonates and/or chemotherapy to synergistically improve palliation. This article reviews the rationale, indications and monitoring of standard-dose samarium and investigational high-dose 153Sm-EDTMP treatment of cancer involving bone.

Animals↗
PubMed1997

[Inhibitory effect of samarium-153-labeled ethylenediaminetetramethylene phosphonate (EDTMP) on bone invasion and osteolysis in Walker 256 carcinoma bearing rats].

OBJECTIVE: To investigate the inhibitory effect of samarium-153 EDTMP on bone invasion and osteolysis in Walker 256 carcinoma bearing rats. METHODS: Invasion and resorption of tibia by Walker 256 carcinoma in rats were evaluated by X-ray and histological examination. RESULTS: Intravenous administration of 153Sm-EDTMP at a dose of 74 or 148 MBq/kg, the rat numbers with tibia invasion and bone resorption were reduced by fifty percent. 153Sm-EDTMP at a dose of 37 MBq/kg still exhibited inhibitory effect on bone invasion and osteolysis as compared with the control group. However, there was no indication of change in the weight of primary tumor even at the highest dose utilized. CONCLUSION: Samarium-153 EDTMP can inhibit bone invasion and osteolysis by Walker 256 carcinoma in rats, but it has no effect on the growth of the transplanted tumor. Therefore, that the effect of 153Sm-EDTMP is due to a reduction in tumor growth leading to decreased bone invasion and osteolysis can be reasonably ruled out.

Animals↗
PubMed1995

Samarium-153-EDTMP for palliation of ankylosing spondylitis, Paget's disease and rheumatoid arthritis.

Samarium-153-EDTMP is an effective agent for palliation of widespread skeletal metastases because it concentrates in bone metastases which have an osteoblastic component. Similar concentration in areas of osteoblastic activity in ankylosing spondylitis, Paget's disease and rheumatoid arthritis suggests a possible new treatment approach. Three patients with ankylosing spondylitis, one patient with Paget's disease and one patient with rheumatoid arthritis were treated with 153Sm-EDTMP. Objective and subjective improvement was noted, especially in ankylosing spondylitis patients. Samarium-153-EDTMP has disease-modifying potential in ankylosing spondylitis and Paget's disease and has palliative value in resistant rheumatoid arthritis. Further trials to determine optimal dose, treatment scheduling, long-term disease-modifying potential and toxicity are needed.

Arthritis, Rheumatoid↗
PubMed1996

Clinical evaluation of a samarium compound filter and E-speed film.

Producing radiographs of good diagnostic quality while keeping the dose as low as possible is the goal of the dental radiographer. Rare earth compound filters reduce the dose, but few clinical studies have evaluated the diagnostic yield. The diagnostic quality of a samarium compound filter used with E-speed film was compared with that of a conventional aluminum filter used with E-speed film. Bitewing projections with the test and standard filters were exposed for 39 patients. Agreement was evaluated with kappa statistics. The results indicated a substantial level of agreement between the two filter types. The combination of samarium compound filter and E-speed film appears to be a good mechanism for achieving dose reduction without compromising the diagnostic yield of the film.

Aluminum↗
PubMed2000

Evidence for ionic samarium(II) species in THF/HMPA solution and investigation of their electron-donating properties

The fundamental nature of samarium(II) complexes in THF/HMPA (HMPA = hexamethylphosphoramide) solutions containing SmI2 has been clarified by means of cyclic voltammetry, conductivity measurements, UV spectroscopy, and kinetic measurements. The principal species is not [SmI2(hmpa)4] as previously suggested, but either the ionic cluster [Sm(hmpa)4(thf)2+2I- if four equivalents of HMPA is present in the THF solution or [Sm(hmpa)6]2+ 2I- in the presence of at least 10 equivalents of HMPA. The formal potential of the [Sm(hmpa)4(thf)2]3+ 2I-/[Sm(hmpa)4(thf)2]2- 2I- redox couple determined by cyclic voltammetry was -1.79 +/- 0.08 V versus SCE. The order of reactivity of the samarium(II) complexes was found to be [Sm(hmpa)6]2+2I- > [Sm(hmpa)4(thf)2]2+2I- > SmI2 in their respective reactions with 1-iodobutane and with benzyl chloride. Very high rate enhancements, of the order of 1,000-15,000-fold, were observed upon addition of HMPA to the THF solution containing SmI2, Comparison of these rate constants with the corresponding rate constants for electron transfer (ET) reactions involving aromatic radical anions revealed that none of the reactions studied can be classified as outer-sphere ET processes and that the inner-sphere electron-donating abilities of the [Sm(hmpa)4(thf)2]2+ 2I- and SmI2 complexes are comparable. The inner-sphere ET character of the transition state increases on going from 1-iodobutane and benzyl bromide to benzyl chloride and acetophenone.

Journal Article↗