Dehydroamino Acids and Dehydrodipeptides Towards N-Bromosuccinimide: Synthesis of β-Bromo- and β,β-Dibromodehydroamino Acid Derivatives and of Substituted 4-Imidazolidinones
摘要:
我们开发了对我们先前报道的用于合成 N,N-二酰基脱氢氨基酸衍生物的高产方法的改进,以制备 N-单保护脱氢氨基酸和脱氢二肽。因此,通过用1当量处理相应的L-丝氨酸、L-苏氨酸和D,L-3-苯基丝氨酸(苏型型)衍生物制备了几种脱氢丙氨酸、脱氢氨基丁酸和脱氢苯丙氨酸衍生物。二叔丁基二碳酸酯和4-(二甲氨基)吡啶。反应进行,最初形成 O-叔丁基碳酸酯,通过用 N,N,N',N'-四甲基胍处理,进行 β 消除,得到相应的脱氢氨基酸衍生物。这种两步法可以作为一锅法进行,并且是立体选择性的,仅给出 Z 异构体。N-单保护的脱氢氨基酸用 N-溴代琥珀酰亚胺处理,然后用三乙胺处理,得到几种 β,β-二溴脱氢丙氨酸或 β-溴-、β-烷基-或 β-芳基脱氢丙氨酸。后者作为 E 和 Z 异构体的混合物获得。使用脱氢苯丙氨酸和使用 4-甲苯磺酰基作为 N-保护基团时,观察到对 Z 异构体形成的立体选择性增加。在脱氢二肽的情况下,当
Asymmetric Synthesis and Reactions of cis-N-(p-Toluenesulfinyl)aziridine-2-carboxylic Acids
摘要:
cis-Aziridine-2-carboxylic acids, 2, precursors of the difficult to prepare syn-beta-hydroxy-alpha-amino acid structural unit, are prepared in high diastereomeric purity by a Darzens-type reaction of the lithium enolate of methyl bromoacetate with enantiopure sulfinimines 1.
Regiospecific Intermolecular Aminohydroxylation of Olefins by Photoredox Catalysis
作者:Kazuki Miyazawa、Takashi Koike、Munetaka Akita
DOI:10.1002/chem.201501590
日期:2015.8.10
A simple and regiospecific aminohydroxylation of olefins by photoredoxcatalysis has been developed. N‐protected 1‐aminopyridinium salts are the key compounds and serve as amidyl radical precursors by the action of Ir photocatalysts, fac‐[Ir(ppy)3] and [Ir(ppy)2(dtbbpy)](PF6) (ppy=2‐pyridylphenyl, dtbbpy=4,4′‐di‐tert‐butyl‐2,2′‐bipyridine). The present photocatalytic system allows for synthesis of
Osmium-catalyzed vicinal oxyamination of olefins by Chloramine-T
作者:K. B. Sharpless、A. O. Chong、Koichiro Oshima
DOI:10.1021/jo00863a052
日期:1976.1
<i>cis</i>-1,2-Aminohydroxylation of Alkenes Involving a Catalytic Cycle of Osmium(III) and Osmium(V) Centers: Os<sup>V</sup>(O)(NHTs) Active Oxidant with a Macrocyclic Tetradentate Ligand
Catalytic activity of [Os-III(OH)(H2O)(L-N4Me2)](PF6)(2) (1: L-N4Me2 = N,N'-dimethyl-2,11-diaza-[3,3](2,6)pyridinophane) in 1,2-cis-aminohydroxylation of alkenes with sodium N-chloro-4-methylbenzenesulfonamide (chloramine-T) is explored. Simple alkenes as well as those containing several types of substituents are converted to the corresponding 1,2-aminoalcohols in modest to high yields. The aminoalcohol products have exclusively cis conformation with respect to the introduced -OH and -NHTs groups. The spectroscopic measurements including cold mass spectroscopic study of the reaction product of complex 1 and chloromine-T as well as density functional theory (DFT) calculations indicate that an oxido-aminato-osmium(V) species [Os-V(O)(NHTs)(L-N4Me2)](PF6)(2) (2) is an active oxidant for the aminohydroxylation. The DFT calculations further indicate that the reaction involves a [3 + 2] cycloaddition between 2 and alkene, and the regioselectivity in the aminohydroxylation of unsymmetrical alkenes is determined by the orientation that bears less steric hindrance from the tosylamino group, which leads to the energetically more preferred product isomer.
A New Approach to Osmium-Catalyzed Asymmetric Dihydroxylation and Aminohydroxylation of Olefins
作者:Malin A. Andersson、Robert Epple、Valery V. Fokin、K. Barry Sharpless