Mirabimide E, an Unusual N-Acylpyrrolinone from the Blue-Green Alga Scytonema mirabile: Structure Determination and Synthesis
摘要:
Mirabimide E, a solid tumor selective cytotoxin from the terrestrial blue-green alga Scytonema mirabile UH strain BY-8-1, possesses an unprecedented tetrachlorinated ethylene group and has been identified as (5S,2'R,3'R)-N- (anti-8/,8',9',9'-tetrachloro-3'-(carbamoyloxy)-2'-methyldecanoyl)-4-methoxy-5-methyl-3-pyrrolin-2-one. The total structure, including absolute stereochemistry, of this novel N-acylpyrrolinone was concluded from a combination of spectral and chemical studies, including stereoselective syntheses of three degradation products, viz. methyl (2R,3R)-anti-8,8,9,9-tetrachloro-3-hydroxy-2-methyldecanoate, (5R,6R)-trans-5-methyl-6-(5,5',6,6'-tetrachloroheptyl-1-oxa- 3-azacyclohexane-2,4-dione, and (5S)-4-methoxy-5-methyl-3-pyrrolin-2-one and the total synthesis of mirabimide E itself. The influence of the carbamate ester group on the chemical degradation and synthesis of mirabimide E is described.
Allyl boron derivatives are valuable building blocks in the synthesis of natural products and bioactive molecules. Herein, a practical strategy of nickel-catalyzed highly selective hydroalkenylation of alkenyl boronicesters was developed. Under the mild reaction conditions, a variety of allyl boronicesters were accessed with excellent chemo- and regioselectivity. The mechanism of this transformation
Synthesis of α-amino ketones through aminations of umpoled enolates
作者:Xiaowen Xia、Bocheng Chen、Xiaojun Zeng、Bo Xu
DOI:10.1039/c8ob02004c
日期:——
An efficient synthesis of α-amino ketones is developed using the umpolung strategy. Umpoled enolates such as N-alkenoxypyridinium salts react smoothly with diverse amines to give α-amino ketones via an SN2′ pathway. This umpolung strategy overcomes the drawbacks of traditional methods such as the need for prefunctionalized ketone derivatives. Our method also offers good chemical yields and high functional
使用umpolung策略开发了α-氨基酮的有效合成方法。诸如N-烯氧基吡啶鎓盐之类的酚醛树脂与各种胺能顺利反应,通过S N 2'途径生成α-氨基酮。这种抗药性策略克服了传统方法的缺点,例如需要预官能化的酮衍生物。我们的方法还具有良好的化学收率和较高的官能团耐受性。
Synthesis of α-Trifluoromethylthiolated and α-Thiocyanated Ketones Using Umpoled Enolates
作者:Xiaowen Xia、Bocheng Chen、Xiaojun Zeng、Bo Xu
DOI:10.1002/adsc.201800968
日期:2018.11.16
An efficient synthesis of α‐trifluoromethylthiolated and α‐thiocynated ketones via Umpolung strategy is developed. Umpoled enolates (N‐alkenoxypyridinium salts) react smoothly with readily available sulfur containing nucleophiles such as AgSCF3 and KSCN using CH3CN as the solvent. N‐alkenoxypyridinium salts could be easily prepared from the gold catalyzed addition of pyridine N‐oxide to alkynes. Our
BrCCl3 and CBr4 was develop, enabling Kharasch-type addition/nucleophilic substitution cascade to selectively produce α-gem-dihalovinyl ketones and chromen-2-ones with moderate to good yields. Use of monoalkynes without additional nucleophilic sites furnished α-gem-dihalovinyl ketonesthrough a Kharasch-type addition and intermolecular allylic substitution cascade whereas the latter transformation of 2-ethynylphenols
employed as electrophilic vinyl sources in complexsynthesis. The triflation of enolates is commonly required for the preparation of vinyl triflates, generally under strongly basic conditions. Herein, the reaction between alkynes and dimethyl(methylthio)sulfonium trifluoromethanesulfonate is presented, which leads to the development of a facile synthesis of β-methylthio vinyl triflates in a chemo-