外消旋木榄醇甲的简捷合成

报道了天然产物木榄醇甲的一种高效合成方法. 目标分子结构中的饱和碳链部分以廉价的化工原料4-羰基戊酸(国内俗称“左旋糖酸”或“果糖酸”)为起始原料合成. 经Wittig反应与间甲氧基苯甲醛相连接后, 对所形成的碳-碳双键进行环氧化并在苄位进行选择性脱氧形成关环前体. 关键的桥环部分结构的建立利用了由缩酮为烷化剂的分子内Friedel-Crafts反应.     

Dynamic NMR study of dinitrophenyl derivatives of seven‐membered cyclic ketals of pyridoxine

Two pyridoxine derivatives containing a dinitrophenyl moiety were investigated by ¹H NMR spectroscopy. Conformational dynamics in solution were studied for each compound using dynamic NMR experiments. It was shown that both compounds studied are involved into two conformational exchange processes. The first process is a transformation of the seven‐membered cycle conformation between the enantiomeric P‐twist and M‐twist forms, and the second is a rotation of the dinitrophenyl fragment of the molecules around the C–O bond. Energy barriers of both conformational transitions were determined. Copyright © 2015 John Wiley & Sons, Ltd.     

Synthesis of a Novel Carbon Based Acid Catalyst and Its Catalytic Activity for the Acetalization and Ketalization

A novel carbon based strong solid acid catalyst has been synthesized successfully. The catalytic activity for acetalization and ketalization was investigated. The results showed that the novel catalyst was very efficient with the average yield over 92%. The novel heterogeneous catalyst also has the advantages of high activity, wide applicability even to the preparation of 7 membered ring acetals and ketals, strikingly simple workup procedure, non-pollution and reusability, which will contribute to the green process greatly.     

CARO'S ACID SUPPORTED ON SILICA GEL. PART VI. A MILD REAGENT FOR REGENERATION OF CARBONYL COMPOUNDS FROM ACETALS,KETALS, AND 1,1-DIACETATES

Efficient conversion of acetals, ketals, and diacetates to carbonyl compounds is described using Caro's acid supported on silica gel. The deacetalization reactions are carried out in acetonitrile at room temperature. Reaction of diacetates is performed in refluxing dichloromethane, and their parent carbonyl compounds are obtained in good-to-excellent yields.     

Xanthone in synthesis: a reactivity profile via directed lithiation of its dimethyl ketal

Xanthone, as its dimethyl ketal, undergoes functionalization with a synthetically useful degree of regioselectivity using a lithiation protocol. The core structure is regenerated during the work-up. Monosubstitution at C-4 or C-1 and disubstitution at C-4 and C-5 or C-1 and C-5 are observed. The substitution pattern appears to be dependent upon the experimental conditions.     

Synthesis of 2,2‐Bis‐C‐functionalized Chain Glucosid‐3‐ketals

Novel 2,2‐bis‐C‐functionalized chain glucosid‐3‐uloses have been synthesized in the form of ketal. The synthesis is rather convenient through one pot multistep reactions and no expensive reagents are involved. The products are formed via autoxidation‐Michael addition mechanism and their structures were characterized by X‐ray crystallographic analysis. Their crystal stuctures are stablilized by intermolecular hydrogen bonds and double‐strand supramolecular stacking is observed.     

(±)-Diinsininone: made nature's way

We report the synthesis of diinsininone (33), the aglycone of (±)-diinsinin (2). Thereby, we complete the first construction of a proanthocyanidin (PA) type-A compound incorporating a [3.3.1]-bicyclic ketal as its characteristic core. Our strategy utilizes a coupling between a benzopyrilium salt and a flavanone that proves applicable to other PA type-A compounds. During this undertaking, treatment of naringenin (9) with 2-iodoxybenzoic acid (IBX) followed by reductive work-up affords eriodictyol (10). This reactivity mirrors that of catechol hydroxylase (F3H) found in the flavonoid pathway. Other interesting transformations include the formation of flavonoids through an ortho-quinone methide (o-QM) cycloaddition-oxidation sequence and regioselective β-glycosidations of several unprotected flavanones suggesting a likely synthesis of 2 from the aglycone 33.     

Towards Total Synthesis of Forskolin I. The Synthesis of Fragment Intermediates A and B

Methods for synthesis of two crucial intermediate A and B starting with 2,4,4-trimethyl-2-cyclo-hexenone 1 and 2,3-dibromofuran 9 are disclosed.     

α,ω-二芳基取代全甲基多硅烷的合成及性质的研究

1964年,Gilman 等人在研究芳基多硅烷的紫外光谱时,认为苯基五甲基二硅烷在231 nm 处的强吸收峰(ε10,900)是由于硅-硅键与苯环共轭,从而使苯的~1La 带红移的结果。尔后,Sakurai 等对此又进行了系统的研究,并提出了分子内电荷转移的机制(σ_(?)→π~*跃迁)。为了进一步了解硅-硅键与π-体     

A Novel Synthesis of 3-O-Allyl-4, 5, 6-tri-O-benzyl-1-O-（p-methoxybenzyl）-D-myo-inositol

Highly efficient synthesis of the entitled compound was achieved from a readily available myo-inositol derivative. The key step involved a desymmetrization with ( )-camphor dimethyl ketal to give two diastereomers. The two diastereomers could be used to synthesize the same compound by changing the orders to introduce the protective groups.