查询词典 aldehydes

The synthesis of the pentacyclic skeleton of Et-743 and the construction of the five chiral centers thereof.1. The core pentacyclic skeleton of phthalascidin was constructed with L-dopa as the starting material via thirteen steps. First, two basic synthons, the C-1 functionalized tetrahydroisoquinoline compounds 8 and N-protected Z-dopa derivative 9, were prepared from L-dopa. They were coupled via amide bond to form the dipeptide compounds 10, which were the first key intermediates. Then the primary hydroxyl groups were transformed into the corresponding amino aldehydes 11 via Swern oxidation. Followed by the intramolecular Pictet-Spengler cyclization, the pentacyclic compounds 12 were synthesized.

五环骨架的构建及五个正确手性中心的确立：1.1我们以L-多巴为起始原料，经过多步官能团保护和转化合成了基本结构单元8然后和苯丙氨酸衍生物9，通过缩合反应生成酰胺中间体10，经Swern氧化得到醛化合物11，然后再次利用分子内改良的Pictet-Spengler反应一步构建c，d两环，得到五环骨架化合物12，最后，实现了21-位羰基向氰基的转化，得到了C-1位官能化的化合物14，化合物14不但具有和Et-743一致的五环骨架，而且分子中五个手性中心立体构型也与其完全相同：其中，3，位和13，位的手性中心由原料L-多巴带入，而1，位，11，位和21，位手性中心则通过不对称诱导而确立。

The reactions of propargyl bromide/sodium iodide and aldehydes and ketones promoted by metallic dysprosium could obtain homopropargyl alcohols in high yield.

炔丙基溴/碘化钠与醛、酮在金属镝促进下可较高产率地得到高炔丙醇化合物。

Seven derivatives of 1,3- dithiocyclohexane were prepared via the reaction o f 7 aldehydes with Bunte′s salt prepared from 1,3-dichloroprop ane and sodium thiosulfate.

国内外关于 1， 3 二硫环己烷类化合物的合成已有大量报道 [5~8]，但反应条件较苛刻，一般都在-18~78℃之间，而且一种方法只能合成一种物质。

Evaluating the effect of the addition of tannin in the stillage and brewing water,the rate of 6g/hl in stillage water and 10g/hl in brewing water under pH 5.3 and 62℃ can be in favor of wort filtrition, restrain LOX reaction, reduce the aldehydes concentration in the wort, enhance the deoxidization, restrain the oxidation of lipid and protein to enhance t...

1在洗糟水加6g/hl，酿造水加10g/hl的单宁，控制pH5.3，温度62℃，既有利于麦汁的过滤、抑制LOX反应、降低麦汁醛类浓度、增强啤酒的还原力，又能抑制脂肪和蛋白质氧化，提高啤酒的风味稳定性。

It was found that the allylide of sulfonium salt could react with aryl aldehydes to afford corresponding trans-epoxides in good yield with good trans/cis selectivity and excellent enantioselectivity.

根据反应条件对反应的影响并结合通过单晶测定的反式环氧化产物的绝对构型，我们提出了氢键起主导作用的手性诱导机制。

After ultra high pressure treatment, limonene concentration was decreased greatly while myrcene and α-pinene concentrations were not changed significantly and the concentration of limonene was decreased by 75% after high pressure treatment of 500 MPa for 15 min,α-terpineol and carvone concentrations were increased significantly. The aldehydes concentrations were retained well. The ester concentrations were changed under high pressure treatment, but generally their concentrations were not changed remarkably.

通过定量检测分析发现：超高压处理对橙汁中的柠檬烯成分影响很显著，经500 MPa的压力处理15 min后其含量下降了75%，而月桂烯和α-蒎烯受高压影响较小；α-松油醇、香芹酮含量经高压处理后迅速增加；醛类特征香气成分基本不受高压影响；酯类成分在高压下会发生变化，但总体变化不显著。

The results showed that there were 8 kinds of aliphatic, 5 kinds of esters, 2 kinds of aldehydes, 2 kinds of nitrogen sulfur heterocyclic rings and one kind of hydrocarbon, alcoholics, ketone, lactones respectively in the analyzed 21 kinds of aroma components, and the content of furfural,β-methyl valeric acid, palmitic acid, nicotine, neohytadiene were higher, next were acetyl ethyl propionate, caleric acid, phenyl ethyl acetate, hydroxylic diethyl succinate.

结果表明，在分析出的21种香气成分中，分别有脂肪酸类8种，酯类5种，醛类2种，氮硫杂环类2种，烃类、醇类、酮类、内酯类各l种，其中相对含量较高的物质成分是糠醛、β-甲基戊酸、十六碳酸、烟碱、新植二烯，其次是乙酰丙酸乙酯、异戊酸、苯乙酸乙酯、羟基丁二酸二乙酯等。

This mechanism is different from that for the acetalization reaction of polyvinyl alcohol with saturated aldehydes,which has only 1,2-addition.Crosslinking in polyvinyl butenal was mainly resulted from the 1,4-addition.

此机理不同于只有1，2-加成方式的聚乙烯醇缩饱和醛化反应。1，4-加成主要导致聚乙烯醇缩丁烯醛的交联。

The acetalization and ketalization of various aldehydes and ketones with catechol by using HY zeolite as catalyst were studied.

研究了 HY分子筛催化邻苯二酚与环己酮、丁酮、丙酮、丙醛、丁醛、异丁醛、戊醛、异戊醛、正己醛、正辛醛、苯甲醛、二苯甲酮等十余种醛的缩合反应。

The acetalization and ketalization of various aldehydes and ketones with glycerol by using KHSO4 as catalyst were studied. Effect of reaction time, mole ratio of reactants and amount of catalyst on yield of acetals were investigated.

研究了在KHSO4催化下，丙三醇与环己酮、丁酮、丙酮、丙醛、丁醛、异丁醛、戊醛、异戊醛、正辛醛、二苯甲酮、苯甲醛等十余种醛的缩合反应。

In the negative and interrogative forms, of course, this is identical to the non-emphatic forms.

。但是，在否定句或疑问句里，这种带有"do"的方法表达的效果却没有什么强调的意思。

Go down on one's knees;kneel down

屈膝跪下。。。下跪祈祷