Concise total synthesis of (+)-carpamic acid

We report herein an efficient enantioselective synthesis of (+)-carpamic acid, with nine steps as the longest linear sequence, the key strategy being based on a novel sequence of a cross-metathesis (CM) reaction and a subsequent cyclizing reductive amination to form the piperidine ring.     

Synthesis of (+)-zeylenone from shikimic acid

Starting from shikimic acid, the total synthesis of zeylenone was studied. The product was proved to be the (+)antipode of zeylenone through analysis and comparison of their respective spectra (including NMR, MS, IR and CD) and optical data. The absolute configuration of the natural product was thus determined to be (1S,2S,3R).     

Synthesis of (+)-puraquinonic acid

(+)-Puraquinonic acid (1a) was synthesized, using a route based on ring-closing metathesis and radical cyclization, the chirality of the quaternary carbon being controlled by a temporary adjacent asymmetric center.     

Synthesis of (+)-salvianolic acid A from sodium Danshensu

(+)-Salvianolic acid A, one of the most active components in the traditional Chinese medicine Danshen, has been synthesized over 10 steps in 6.5% overall yield. Starting from inexpensive ortho-vanillin and sodium Danshensu (synthesized via asymmetric catalysis in our group), the process consists of the following: A Wittig reaction that gives the desire product with absolute E-configuration, a demethylation reaction with AlCl₃ in a satisfactory yield, and a practical deprotection of allylic groups to afford the terminal product (+)-salvianolic acid A. The current synthetic technology possesses the advantages of using inexpensive starting materials, mild reaction conditions and has the potential for use in large scale synthesis.     

Synthesis of (+)-lagerstronolide from (+)-sclareol

The γ-acetoxybutenolide (+)-lagerstronolide was synthesized from (+)-sclareol, with an overall yield of 10%. The absolute stereochemistry for the natural compound (−)-lagerstronolide has been correctly established.     

Synthesis of (+)-perillyl alcohol from (+)-limonene

(+)-Perillyl alcohol (1) has been synthesised in four steps and 39% overall yield from commercially available limonene oxide (4). The sequence features, as its key step, a palladium(0)-mediated transformation of a secondary allylic acetate (6) into its primary isomer (7). An application of (+)-perillyl alcohol (1) in a formal synthesis of naturally occurring (−)-mesembrine (2) and (−)-mesembranol was demonstrated.     

Synthesis of (+)-agelasine D from (+)-manool

(+)-Agelasine D, originally isolated from the marine sponge Agelas nakamurai, is synthesized for the first time. The terpenoid side chain was readily available from the diterpene alcohol (+)-manool.     

Synthesis of (+)-pechueloic acid and (+)-aciphyllene. Revision of the structure of (+)-aciphyllene

1αH,7αH,10αH-Guaia-4,11-dien-3-one and its 1βH,10βH diastereomer, easily obtained from (+)-dihydrocarvone, are good starting materials for the synthesis of natural guaiane derivatives. Allylic oxidation of the 1αH,10αH isomer gave as main product its 13-hydroxy derivative and a small amount of (+)-7β-hydroxy-1αH,10αH-guaia-4,11-dien-3-one, whereas the 1βH,10βH diastereomer afforded selectively the (−)-7α-hydroxy-1βH,10βH enantiomer in excellent yield. From the 13-hydroxy derivative (+)-pechueloic acid and (+)-methyl pechueloate were synthesized. Deoxygenation at C₃ of the 1βH,10βH guaiadienone afforded a guaiadiene with the reported structure for aciphyllene but its spectral data did not agree with those reported for the natural diene. The structure of natural (+)-aciphyllene has been corrected to 1αH,7αH,10αH-guaia-4,11-diene obtained by deoxygenation of the 1αH,10αH guaiadienone.     

Synthesis of (+)-negamycin from D-glucose

The broad spectrum antibiotic (+)-negamycin (1) was prepared from 1,2-O-isopropylidene-d-glucose (3) in nine steps.     

(+)-Trans-chrysanthemic acid from (+)-Δ3-carene

A new and more efficient route for the conversion of the readily available (+)-Δ³-carene into (+)-trans-chrysanthemic acid is described.     

Synthesis of ethers of (+)-usninic acid pyrazole derivatives

The reduction of usninic acid pyrazole derivatives by complex boron hydrides under various conditions was studied. New ether derivatives containing added alcohols were obtained upon reduction of the carbonyl. The reaction occurred presumably through a quinonemethide intermediate.     

(+)-2-甲基-4-戊烯酸的合成

丙二酸二乙酯与碘甲烷反应生成二乙基甲基丙二酸酯(1). 由(1)进行皂化和脱羧反应制备2-甲基-4-戊烯酸(4).用一种新的拆分剂葡辛胺拆分(4)得到(+)-2-甲基-4-戊烯酸.     

Synthesis of (+)-drim-8-en-11-oic acid

A four-stage synthesis of (+)-drim-8-en-11-oic acid (IX) from norambreinolide (II) has been developed. The latter was converted by boiling with ethanolic sulfuric acid into a mixture of the methyl esters of bicyclohomofarnes-7- and -8-enoic acids which, on reaction with methyllithium, gave a mixture of 12-methyl-14,15,16-trinorlabd-7-and -8-en-12-ols. The alcohol with the ⁸ double bond was dehydrated with p-toluenesulfonic acid to 11-methyl-14,15,16-trinorlabd-8,11-diene, the ozoization of which yielded (+)-drim-8-en-11-oic acid.Institute of Chemistry, Academy of Sciences of the Moldavian SSR, Kishinev. Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 214–221, March–April, 1991.     

Reactive enols in synthesis 2. Synthesis of (+)-latifolic acid and (+)-latifoline

We describe a short, enantioselective synthesis of the naturally occurring pyrrolizidine alkaloid (+)-latifoline (1) employing a tandem [3,3] sigmatropic rearrangement/[1,2] allyl shift as a key step in constructing (+)-latifolic acid (4).     

Synthesis of new peptidic glycoclusters derived from β-alanine

The synthesis of an asymmetric glycocluster 1 has been achieved by coupling of a sugar unit with the β-alanine polypeptide, the principal chain, and combining a carbohydrate chain with the side chain causing it to branch from the N terminal. The synthesis of this side chain multivalent ligands is based on the scaffolding of some ω-amino acid (glycine, β-alanine, and GABA) derivatives. This method facilitated the synthesis of the cluster, of which the length of each unit differs.     

从青藤碱制备具有(＋)-C-Normorphinan骨架的化合物

对青藤碱进行Mitsunobu甲基化反应, 得到O-甲基青藤碱(2); 2经过酸性水解、硼氢化还原以及高碘酸钠氧化开环得到O-甲基青藤碱二醛(5); 在哌啶存在下对5进行羟醛缩合反应, 区域选择性地闭环生成具有(＋)-C-normorphinan骨架的化合物(8S,12S,13R)-6,7-didehydro-3,4-dimethoxy-16-methyl-C-normorphinan-7-carboxaldehyde (7); 经过以上五步反应, 7的总收率约35%. 对7进行硼氢化还原得到化合物8; 化合物8以醋酐进行酯化得到化合物9. 化合物7以5% Pd/C为催化剂、1.01×105 Pa下与氢气作用发生双键氢化反应, 立体定向地得到化合物10, 从化合物10出发获得化合物11和12. 通过对化合物11的1H NMR, 13C NMR, 2D-NMR及NOESY等核磁共振分析确定化合物10, 11和12具有7S绝对构型.