alkyl, aryl) positions and affords essentially single diastereomeric products with enantioselectivities higher than 95 % ee in most cases. Among the bifunctional Brønsted base/H‐bond catalysts examined, a known squaramide–tertiary amine catalyst and a newly prepared squaramide–tertiary amine catalyst provide the highest selectivity so far with either nitroolefins or vinyl ketones as the acceptor components
在有机催化迈克尔反应方法的基础上,开发了一种新的对映选择性合成5,5-二取代(季)乙内酰脲的方法,该方法涉及使用2-苄硫基-3,5-二氢咪唑-4-酮作为主要的乙内酰脲替代物。该方法是关于乙内酰脲的N 1(烷基,芳基,酰基),N 3(芳基)和C 5(直链/支链烷基,芳基)位置的取代方法的一般方法,并提供具有较高对映选择性的基本非对映体产物高于95% ee在多数情况下。在所研究的双功能布朗斯台德碱/氢键催化剂中,以硝基烯烃或乙烯基酮为受体组分,已知的方胺-叔胺催化剂和新制备的方胺-叔胺催化剂提供了迄今为止最高的选择性。动力学测量结果支持了一级反应速率对两个反应伙伴,供体模板和迈克尔受体的依赖性,而竞争性1 H NMR光谱实验表明模板具有很高的催化剂结合能力。
Asymmetric Synthesis of Adjacent Tri‐ and Tetrasubstituted Carbon Stereocenters: Organocatalytic Aldol Reaction of an Hydantoin Surrogate with Azaarene 2‐Carbaldehydes
作者:June Izquierdo、Noémie Demurget、Aitor Landa、Tore Brinck、Jose M. Mercero、Peter Dinér、Mikel Oiarbide、Claudio Palomo
DOI:10.1002/chem.201902817
日期:2019.9.20
A bifunctional amine/squaramide catalyst promoted direct aldol addition of an hydantoin surrogate to pyridine 2-carbaldehyde N-oxides to afford adducts bearing two vicinal tertiary/quaternary carbons in high diastereo- and enantioselectivity (d.r. up to >20:1; ee up to 98 %) is reported. Acid hydrolysis of adducts followed by reduction of the N-oxide group yields enantiopure carbinol-tethered quaternary
Among the Missing: Content on Lesbian and Gay People in Social Work Journals
作者:R. Van Voorhis、M. Wagner
DOI:10.1093/sw/47.4.345
日期:2002.10.1
Lesbian and gay issues are barely visible in the social work literature. This study examined the content of articles on homosexuality that were published in four major social work journals between 1988 and 1997. Articles were coded according to their focus on either HIV/AIDS and the gay community or other issues pertaining to lesbians and gay men. Articles were also coded as client focused, worker focused, or macro focused. Two-thirds of the 77 articles published on homosexuality focused on HIV/AIDS. Most articles reflected a problem-oriented view of gay and lesbian people; few addressed heterosexism or environmental interventions. More literature is needed that focuses on strengths, heterosexist conditions, and social justice for lesbian and gay people.
Chiral analysis of the reaction stages in the Edman method for sequencing peptides
作者:John S. Davies、A. Karim A. Mohammed
DOI:10.1039/p29840001723
日期:——
Chiral isothiocyanate reagents suitable for ‘Edmansequencing’ have been synthesised and used to assess the chiral features of individual stages in the Edmanmethod. Using h.p.l.c. analysis of the diastereoisomeric thiohydantions obtained, it has been deduced that the cyclisation and cleavage of thiazolinone step is the likely source of racemisation of the chiral centre derived from the N-terminal
5,5-diaryl and 5-alkyl-3-phenyl-4-imidazolidones: A novel synthesis
作者:Jitender M. Khurana、Arpita Agrawal、Geeti Bansal
DOI:10.1002/jhet.165
日期:2009.9
Synthesis of 5,5-diaryl and 5-alkyl-3-phenyl-4-imidazolidones has been reported by reductive desulfurization of 5,5-diaryl and 5-alkyl-3-phenyl-2-thiohydantoins with nickel boride. J. Heterocyclic Chem., (2009).