ZrCl<sub>4</sub> as an Efficient Catalyst for a Novel One-Pot Protection/Deprotection Synthetic Methodology
作者:Surendra Singh、Colm D. Duffy、Syed Tasadaque A. Shah、Patrick J. Guiry
DOI:10.1021/jo800932t
日期:2008.8.1
found to be an efficientcatalyst for the one-pot esterification and deprotection of (5S,6R)-5,6-diacetoxyoct-7-enoic acid in good yields (44−62%) with a lactone formed as a minor byproduct. ZrCl4 (10−20 mol %) was also sufficient to deprotect 1,3-dioxalane, bis-TBDMS ethers, and diacetate functional groups in excellent yields of up to 93%. ZrCl4 (1−10 mol %) also promoted diol protection as the acetonide
A carbohydrate based approach towards the synthesis of aspercyclide C
作者:C.V. Ramana、Mohabul A. Mondal、Vedavati G. Puranik、Mukund K. Gurjar
DOI:10.1016/j.tetlet.2007.08.050
日期:2007.10
A formal totalsynthesis of aspercyclide C (3) is described in which d-ribose is employed as a chiral pool material. The key step is a ring closing metathesis.
Diisopropyl tartrate modified (E)-γ-[(cyclohexyloxy)dimethylsilyl]- and (E)-γ-(dimethylphenylsilyl)allylboronates: Chiral Reagents for the Enantio- and Diastereoselective synthesis of anti 1,2-diols and 2-butene-1,4-diols via the formal α- and γ-hydroxyallylation of aldehydes
作者:William R. Roush、Paul T. Grover
DOI:10.1016/s0040-4020(01)88869-4
日期:1992.1
Enantioselective synthesis of 4-substituted (E)-2-butene-1,4-diols and anti 1,2-diols are described. Highly diastereoselective reactions of aldehydes and the chiral PhMe2Si- and (C6H11O)Me2Si- substituted allylboronates 25 and 26 provide anti homoallylic 29 and 50, respectively. Epoxidation of 29 with dimethyl dioxirane followed by acid catalyzed Petersen rearrangement of the intermediate epoxysilanols
描述了4-取代的(E)-2-丁烯-1,4-二醇和抗1,2-二醇的对映选择性合成。醛与手性PhMe 2 Si-和(C 6 H 11 O)Me 2 Si-取代的烯丙基硼酸酯25和26的高度非对映选择性反应分别提供反均聚物29和50。29用二甲基二环氧乙烷环氧化,然后经酸催化的中间体环氧硅烷醇进行Petersen重排,可得到具有优异对映选择性(81-87%ee)的1,4-丁二醇27。Tamao氧化50提供抗二醇22(ee的64–72%)。这些程序尤其在与一系列氧化的手性醛进行双不对称反应时获得了优异的结果(图1和2)。这些方法有望用于非环状前体糖的非对映选择性合成中。
作者:Timothy P. O'Sullivan、Karl S. A. Vallin、Syed Tasadaque Ali Shah、Jérôme Fakhry、Paola Maderna、Michael Scannell、Andre L. F. Sampaio、Mauro Perretti、Catherine Godson、Patrick J. Guiry
DOI:10.1021/jm060270d
日期:2007.11.1
aromatic LXA4 and LXB4 analogues by employing Sharpless epoxidation, Pd-mediated Heck coupling, and diastereoselective reduction as the key transformations. Subsequent biological testing has shown that these analogues display potent biological activities. Phagocytic clearance of apoptotic leukocytes plays a critical role in the resolution of inflammation. Both LXA4 analogues (1R)-3a and (1S)-3a were
4,5-Diisopropyl-<i>B</i>-[(<i>E</i>)-[(3‘-menthofuryl)dimethylsilyl]allyl]-1,3,2- dioxaborolane, an Improved Chiral Reagent for the Anti α-Hydroxyallylation of Aldehydes: Application to the Enantioselective Synthesis of (−)-Swainsonine
作者:J. A. Hunt、William R. Roush
DOI:10.1021/jo961840s
日期:1997.2.1
Diisopropyl tartrate-modified (E)-[gamma-(furyldimethylsilyl)allyl]boronates 10 and 11 were designed for the enantioselective synthesis of substituted anti-3,4-dihydroxy-1-butenes 9 via the anti-alpha-hydroxyallylation of aldehydes. The reactions of aldehydes with 10 and 11 provided furyldimethylsilyl-substituted anti-1,2-silanols 12 and 13 with good enantioselectivity (74-82% ee), and the silanols were oxidized to the corresponding anti-1,2-diols 9 by a modified Fleming-Tamao oxidation protocol. The high reactivity of the (menthofuryl)silane unit toward electrophilic substitution allowed complete protodesilylation of menthofuryl-substituted silanols 13 and subsequent oxidation to diols 9 in a one-pot operation without competing protodesilylation of the allylsilane unit. However, a two-step protocol was required for the protodesilylation-oxidation of the less reactive 2-(5-methyl)-asymmetric reactions with three chiral aldehydes 23-35 (80 to >92% de, with the exception of the mismatched reactions with aldehyde 25, which were essentially unselective). However, [[[2-(5-methylfuryl)]dimethylsilyl]ally]boronate 10 could only be synthesized in less than or equal to 15% yield, and oxidations of the 2-(5-methylfuryl)-substituted silanols 12 were lower-yielding than oxidations of the corresponding menthofuryl-substituted silanols 13. Thus diisopropyl tartrate-modified (E)-[gamma-[(menthofuryl)dimethylsilyl]ally]boronate 11 proved to be the more useful of the two reagents. As a demonstration of the utility of 11 in the synthesis of polyhydroxylated natural products, this new reagent was used in a brief and highly stereoselective synthesis of the naturally occurring alkaloid (-)-swainsonine (42).