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1.
James P. Kutney Peter Grice Krystyna Piotrowska Steven J. Rettig Jerzy Szykula James Trotter Loc Van Chu 《Helvetica chimica acta》1983,66(6):1820-1826
The thujone-derived enone 1 , upon base-catalyzed reaction with 2-methyl-6-vinylpyridine is converted to the pyridine analogue 5 (Scheme 1). Catalytic reduction of the latter to 6 generates two new centers of chirality which eventually become C(8) and C(14) in the ultimate synthetic steroid analogue 12 . An X-ray analysis of 6 establishes the structure and absolute configuration so as to determine its suitability in subsequent synthetic studies. The acetal derivative 7 , via Birch reduction, hydrolysis, and internal aldol cyclization, is converted into the cyclohexenone analogue 10 (Scheme 2). This ‘one-pot’ process affords an efficient conversion of the pyridine ring into a cyclohexenone system required for A-ring construction of the steroid skeleton. Finally, conversion of 10 , via the unsaturated diketone 11 , provides the chiral steroid analogue 12 . 相似文献
2.
3.
A simple model, consisting of ‘two-body’ reactant and product trajectories joined by an instantaneous switch, is proposed for the alkali atom-alkyl iodide rebound reactions. The electronic potential surfaces governing these trajectories are justified in terms of the electron jump model. Encouraging overall agreement is found with extensive molecular beam data for the K, Cs + CH3I reactions. 相似文献
4.
Dan Lee Leanne Leer Shara Pilch Yu Yasufuku 《Proceedings of the American Mathematical Society》2001,129(11):3193-3200
We find necessary and sufficient conditions for a complete local ring to be the completion of a reduced local ring. Explicitly, these conditions on a complete local ring with maximal ideal are (i) or , and (ii) for all , if is an integer of , then .
5.
6.
Milton J. KiefelPradeep Chopra Paul D. MadgeAlex Szyczew Robin J. ThomsonI. Darren Grice Mark von Itzstein 《Tetrahedron letters》2011,52(1):98-100
Sialic acids are 9-carbon acidic sugars involved in a number of important biological processes and human diseases. As part of our ongoing interest in the development of novel sialic acids as biological probes, we have developed an efficient and simple synthesis of C-9 oxidised sialic acid derivatives. The key oxidative step involves the use of TEMPO under carefully controlled aqueous pH conditions. 相似文献
7.
Tran AB Melly GC Doucette R Ashcraft B Sebren LJ Havko N Young JC O'Neil GW 《Organic & biomolecular chemistry》2011,9(22):7671-7674
A convergent and scalable synthesis of the archazolid western hemisphere has been completed. The V-ATPase inhibitory activity of this compound along with a previously prepared eastern domain was then tested using a convenient Arabidopsis-based V-ATPase assay. 相似文献
8.
Ab initio calculations for the t-butyl radical, (CH3)3C· suggest that it is planar, and that it has a greater resistance to out-of-plane bending than has the methyl radical. The calculated isotropic hyperfine coupling to 13C is +36·8 G for the rigid molecule, together with +32 G for the zero-point vibratory contribution, giving a predicted total of +68·8 G. The experimental isotropic coupling of 46–51 G cannot, therefore, be taken as providing evidence for a pyramidal ground state for this radical. 相似文献
9.
Many aquatic species such as dolphins and whales have fins, which can be modeled as swept wings. Some of these fins, such as the dorsal fin of a dolphin, are semi-rigid and therefore can be modeled as a rigid swept wing with a compliant surface. An understanding of the hydrodynamics of the flow past swept compliant surfaces is of great interest for understanding potential drag reduction mechanisms, especially since swept wings are widely used in hydrodynamic and aerodynamic design. In this paper, the flow past a swept wing with a compliant surface is modeled by an attachment-line boundary layer flow, which is an exact similarity solution of the Navier–Stokes equations, flowing past a compliant surface modeled as an elastic plate. The hydrodynamic stability of the coupled problem is studied using a new numerical framework based on exterior algebra. The basic instability of the attachment line boundary layer on a rigid surface is a traveling wave instability that propagates along the attachment line, and numerical results show that the compliance results in a substantial reduction in the instability region. Moreover, the results show that, although the flow-field is three-dimensional, the qualitative nature of the instability suppression is very similar to the qualitative reduction of instability of the two-dimensional Tollmien–Schlichting modes in the classical boundary-layer flow past a compliant surface. 相似文献
10.
Compound 5 reacted with silver perchlorate in anhydrous benzene to give 3a and in wet acetone to give a mixture of 9 and 10; treatment of 9 with potassium t-butoxide in dimethyl sulphoxide gave 11. 相似文献