Practical Synthesis of 3β-Amino-5-cholestene and Related 3β-Halides Involving <i>i</i>-Steroid and Retro-<i>i</i>-Steroid Rearrangements

Sun, Qi; Cai, Sutang; Peterson, Blake R.

doi:10.1021/ol802343z

Cited by 52 publications

(68 citation statements)

References 27 publications

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“…However, good conversion of the secondary alcohol b-cholesterol was obtained ( Table 2, entry 6), most likely through neighbouring-group participation of the double bond, as earlier observed for bromide introduction into the corresponding b-mesylate. [29] The high stereoselectivity observed is a remarkable advantage of the previously mentioned poor reactivity in a sterically demanding S N 2 reaction, especially considering the fact that formation of 3-bromocholest-5-ene by a classic Appel reaction normally gives mixtures of stereoisomers. [30] After establishing the optimal conditions for bromination, we turned our attention to the introduction of chloride.…”

Section: Wwwchemeurjorgmentioning

confidence: 98%

In Situ Phosphine Oxide Reduction: A Catalytic Appel Reaction

Kalkeren

Leenders

Hommersom

et al. 2011

Chemistry A European J

162

121

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Several important reactions in organic chemistry thrive on stoichiometric formation of phosphine oxides from phosphines. To avoid the resulting burden of waste and purification, cyclic phosphine oxides were evaluated for new catalytic reactions based on in situ regeneration. First, the ease of silane-mediated reduction of a range of cyclic phosphine oxides was explored. In addition, the compatibility of silanes with electrophilic halogen donors was determined for application in a catalytic Appel reaction based on in situ reduction of dibenzophosphole oxide. Under optimized conditions, alcohols were effectively converted to bromides or chlorides, thereby showing the relevance of new catalyst development and paving the way for broader application of organophosphorus catalysis by in situ reduction protocols.

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Section: Wwwchemeurjorgmentioning

confidence: 98%

In Situ Phosphine Oxide Reduction: A Catalytic Appel Reaction

Kalkeren

Leenders

Hommersom

et al. 2011

Chemistry A European J

162

121

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“…This sterol has recently been synthesized (32). A fluorescent conjugate of aminocholesterol was successfully used in a high-throughput screening assay for sterol efflux in cell systems (33).…”

Section: Introductionmentioning

confidence: 99%

Interaction of 3β-Amino-5-cholestene with Phospholipids in Binary and Ternary Bilayer Membranes

et al. 2011

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3β-Amino-5-cholestene (aminocholesterol) is a synthetic sterol whose properties in bilayer membranes have been examined. In fluid palmitoyl sphingomyelin (PSM) bilayers, aminocholesterol and cholesterol were equally effective in increasing acyl chain order, based on changes in diphenylhexatriene (DPH) anisotropy. In fluid 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) bilayers, aminocholesterol ordered acyl chains, but slightly less efficiently than cholesterol. Aminocholesterol eliminated the PSM and DPPC gel-to-liquid crystalline phase transition enthalpy linearly with concentration, and the enthalpy approached zero at 30 mol% sterol. Whereas cholesterol was able to increase the thermostability of ordered PSM domains in a fluid bilayer, aminocholesterol under equal conditions failed to do this, suggesting that its interaction with PSM was not as favorable as cholesterol’s. In ternary mixed bilayers, containing 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC), PSM or DPPC, and cholesterol at proportions to contain a liquid-ordered phase (60:40 by mol of POPC and PSM or DPPC, and 30 mol% cholesterol), the average life-time of trans parinaric acid (tPA) was close to 20 ns. When cholesterol was replaced with aminocholesterol in such mixed bilayers, the average life-time of tPA was only marginally shorter (about 18 ns). This observation, together with acyl chain ordering data, clearly shows that aminocholesterol was able to form a liquid-ordered phase with saturated PSM or DPPC. We conclude that aminocholesterol should be a good sterol replacement in model membrane systems for which a partial positive charge is deemed beneficial.

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“…The copper-catalyzed azide-alkyne cycloaddition (CuAAC) has been used by Paixão et al for the synthesis of 1,2,3-triazoles containing a steroidal moiety. 21 In order to get the best reaction conditions for the 1,3-dipolar cycloaddition of phenylacetylene with the azidocholesterol 58 22 the reaction was carried out in a mixture of THF-H2O (1:1) in the presence of 10 mol% Cu(OAc)2·H2O and sodium ascorbate (20 mol%) (Scheme 13). The desired product 60a was obtained in quantitative yield.…”

Section: Page 206mentioning

confidence: 99%