A double ring closing metathesis reaction in the rapid, enantioselective synthesis of NK-1 receptor antagonists

[structure: see text]. The NK-1 receptor antagonist 1 has been prepared in seven steps from phenylglycine methyl ester. The key steps are a double ring closing metathesis reaction of tetraene 7 to prepare spirocycle 6 and a reductive Heck reaction to introduce the aryl moiety. This latter reaction discriminates the olefins of compound 6 and proceeds in a highly regio- and stereoselective manner.     

ICP-AES法测定内蒙古地区六种沙生木本植物中金属元素

采用ICP-AES法分别对内蒙古地区梭梭、小叶锦鸡儿、沙冬青、红柳、沙枣和沙柳等六种沙生木本植物中金属元素进行了测定和分析。该方法的加标回收率为94.98％～120.25％,RSD＜3.4％,具有良好的准确度和精密度。结果表明,常量元素Ca,K,Mg,Na,Al及植物生命活动所必需的微量元素Fe,Mn,Cu,Zn在六种沙生木本植物中表现为不同的含量顺序,且Fe,Mn,Cu,Zn四种元素的含量均低于陆生高等植物的平均含量。该测定结果为改善西部地区生态环境,选择优良防风固沙树种提供可靠的数据和理论依据。     

Photoinduced trap generation at the Si-SiO2 interface

2 interface upon irradiation of oxidized Si(100) and Si(111) samples with femtosecond laser pulses of nanojoule pulse energy at the wavelength of 780 nm (1.6 eV). We attribute this effect to a dc-field-induced SH contribution which results from the creation of new oxide traps by a photoinduced damage process. The damage process occurs, with a significantly lower efficiency, also under cw irradiation; the experimental results, however, rule out a thermal origin of the effect as well as a multiphoton effect. Received: 11 July 1997     

Crystallization-induced diastereoselection: asymmetric synthesis of substance P inhibitors

A novel three-component condensation followed by a crystallization-induced asymmetric transformation is used to build this key substance P inhibitor intermediate in a short synthetic sequence.     

A practical and efficient preparation of the releasable naphthosultam side chain of a novel anti-MRSA carbapenem

A practical large-scale synthesis of the naphthosultam-based side chain of the anti-MRSA antibiotic 1 has been achieved in 29% overall yield over seven steps from 1-methylnaphthalene. The synthesis was completed without the use of protecting groups, featuring a novel naphthosultam annelation, a chemoselective acid-catalyzed triflation, and the use of a novel naphthosultam dianion to effect functionalization through benzylic metalation.     

An effective synthesis method for secondary fluorinated alcohols via the reaction of esters of polyfluorinated acids with trialkylalanes

Unlike nonfluorinated analogs, complex esters of polyfluorinated acids in reactions with trialkylalanes produce only polyfluorinated secondary alcohols.Department of Fine Organic Synthesis, Institute of Organic Chemistry, Urals Branch, Russian Academy of Sciences, 450054 Ufa. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 10, pp. 2339–2341, October, 1992.     

Asymmetric synthesis of 1,2,3-trisubstituted cyclopentanes and cyclohexanes as key components of substance p antagonists

An efficient asymmetric synthesis of 1,2,3-trisubstituted cyclopentanes and cyclohexanes is described. Three methods were developed for the preparation of the 2,3-disubstituted cyclopentenones and cyclohexenones, which are key achiral building blocks. These intermediates are reduced catalytically with (R)-2-methyloxazaborolidine in high yield (82-98%) and excellent ee (89-96%). Directed reduction of the chiral allylic alcohols using Red-Al gives exclusively the 1,2-anti stereochemistry (>99:1). Epimerization of the ester center followed by saponification/crystallization affords the desired hydroxyacids in good yield (65-70%) and in high enantiomeric excess (>99%).     

Practical synthesis of the calcimimetic agent, cinacalcet

A practical synthesis of cinacalcet (Sensipar^®, Mimpara^®) is described. The synthesis starts from readily available starting materials and relies on safe and practical reaction conditions. The sequence comprises three synthetic steps and only one isolation point. The overall yield for the sequence is 85%.