Total synthesis of (-)-indolactam V

The total synthesis of protein kinase C activator (-)-indolactam V (IL-V) has been successfully completed with two separate approaches: From known 4-nitrotryptophan derivative 3 in 8 steps (49% overall yield) and from L-glutamic acid in 12 steps (18% overall yield), where 4-nitrotryptophanol derivative 4 served as a key intermediate. Derivatives 3 and 4, both incorporating indole 4-substitution and the C-9 stereocenter in IL-V, were synthesized via the Pd-catalyzed indole synthesis from 3-nitro-2-iodoaniline 5 with aldehydes 6 and 7, respectively. Aldehyde 7 was, meanwhile, synthesized from l-glutamic acid in 5 steps (68% yield). Lactamization of the 9-membered ring was achieved using HATU in THF in good yield.     

Total synthesis of the tricyclic marine alkaloids (-)-lepadiformine, (+)-cylindricine c, and (-)-fasicularin via a common intermediate formed by formic acid-induced intramolecular conjugate azaspirocyclization

A very short and efficient enantioselective total synthesis of the tricyclic marine alkaloids (-)-lepadiformine (3), (+)-cylindricine C (1c), and (-)-fasicularin (4) has been developed utilizing the formyloxy 1-azaspiro[4.5]decane 5 as a common intermediate. The key strategic element for the synthesis was the formic acid-induced intramolecular conjugate azaspirocyclization, which proved to be a highly efficient and stereoselective way to rapid construction of the 1-azaspirocyclic substructure of these natural products in a single operation. Thus, the common intermediate 5, synthesized in two steps with 70% overall yield starting from the known (S)-N-Boc-2-pyrrolidinone 7 via the conjugate spirocyclization using an acyclic ketoamide 6, was utilized for the concise and stereoselective total synthesis of (-)-lepadiformine (3), which was accomplished in seven steps with 45% overall yield from 5 (31% yield from 7). The developed strategy based on the conjugate spirocyclization was also applied to the stereoselective total synthesis of (+)-cylindricine C (1c), which was achieved in 10 steps from 5 in 18% overall yield (12% yield from 7). Further application of this approach using 5 led to the synthesis of (-)-fasicularin (4), wherein an extremely efficient method for the introduction of the thiocyanato group via an aziridinium intermediate at the last step was developed. Thus, the highly efficient first enantioselective total synthesis of (-)-fasicularin was accomplished in nine steps with an overall yield of 41% from 5 (28% yield from 7).     

RAFT-mediated emulsion polymerization of vinyl acetate: a challenge towards producing high molecular weight poly(vinyl acetate)

The preparation of poly(vinyl acetate) with well-controlled structure has received a great deal of interest in recent years because of a large number of developments in living radical polymerization techniques. Among these techniques, the use of reversible addition–fragmentation chain transfer (RAFT)-mediated polymerization has been employed for the controlled polymerization of vinyl acetate due to the high susceptibility of this monomer towards chain transfer reactions. Here, a novel water-soluble N,N-dialkyl dithiocarbamate RAFT agent has been prepared and employed in the emulsion polymerization of vinyl acetate. The kinetic results reveal that the polymerization nucleation mechanism changes from homogeneous to micellar and RAFT-generated radicals can change the kinetic behavior from conventional emulsion polymerization to living radical polymerization. At higher concentrations of the modified RAFT agent, as a result of an aqueous phase reaction between RAFT and sulfate radicals, relatively more hydrophobic radicals are generated, which favors entry and propagation into micelles swollen with monomer. This observation was determined from the investigation of the polymerization rate and measurements of the average particle diameter and the number of particles per liter of the aqueous phase. Molecular weight analysis also demonstrated the participation of the RAFT agent in the polymerization in such a way as to restrict chain transfer reactions. This was determined by examining the evolution of polymer chain length and attaining higher molecular weights, even up to 50?% greater than the samples obtained from the conventional emulsion polymerization of vinyl acetate in the absence of the synthesized modified RAFT agent.     

Picolinamide-Cu(Ac)2-imprinted polymer with high potential for recognition of picolinamide-copper acetate complex

In this report, with semi-empirical quantum method, we have studied the conformation and energy of supermolecule composed of picolinamide and its positional isomers with methacrylic acid. We tried to explore the reason why picolinamide was not likely to show imprinting effect when using methacrylic acid as functional monomer in our previous work. In order to produce imprinting effect, which was not achieved based on hydrogen bonding interaction, we have synthesized a molecular-imprinted polymer (MIP) based on copper ion coordination in prepolymerization. The complex in prepolymerization was composed of copper(II), acetate, picolinamide and 4-vinylpyridine (4-Vpy). Suprisingly, the MIP had high selectivity to picolinamide-copper acetate complex, and changes of either copper ion, picolinamide or acetate would result in decrease in the imprinting effect. This is also the first example where the high selective recognition of the MIP to its template was achieved mainly by inhibiting the binding of non-template rather than enhancing the binding of the template. And this report can be also looked upon as a first step towards the solution to the problem of imprinting of template that contains intramolecular hydrogen bond.     

Palladium-catalyzed asymmetric allylic substitution of 2-arylcyclohexenol derivatives: asymmetric total syntheses of (+)-crinamine, (-)-haemanthidine, and (+)-pretazettine

Much interest has been shown in Amaryllidaceae alkaloids as synthetic targets due to their wide range of biological activities. Over 100 alkaloids have been isolated from members of the Amaryllidaceae family; most of them can be classified into eight skeletally homogeneous groups. We have succeeded in the first asymmetric total syntheses of the crinane-type alkaloids (+)-crinamine (1), (-)-haemanthidine (2), and (+)-pretazettine (3). The starting cyclohexenylamine 14 was obtained from allyl phosphonate 11c by palladium-catalyzed asymmetric amination in 82% yield and with 74% ee. The product was recrystallized from MeOH. Interestingly, (-)-14 with 99% ee was obtained from the mother liquor (74% recovery). Intramolecular carbonyl-ene reaction of (-)-10 proceeds in a highly stereoselective manner to give hexahydroindole derivative 9 as the sole product. In the Lewis-acid-catalyzed carbonyl-ene reaction, an interesting rearrangement product, 20, was isolated in high yield. From 9, (+)-crinamine was synthesized. Thus, the asymmetric total synthesis of (+)-crinamine was achieved in 10 steps from 11c, and the overall yield is 19%. The total synthesis of (-)-haemanthidine was also achieved from 9 by a short sequence of steps.     

Efficient and selective synthesis of siphonarienolone and related reduced polypropionates via Zr-catalyzed asymmetric carboalumination

[reaction: see text] Siphonarienolone (1) has been synthesized from siphonarienal (3) in 66% over four steps. Synthesis of 3, in turn, has been achieved in two steps (85% combined yield) from 4, prepared from 3-buten-1-ol in seven steps (23% combined yield). Also, a two-step conversion of 3 into siphonarienone (2) is reported.     

Total synthesis of the microtubule-stabilizing agent (-)-laulimalide

[structure: see text] The total synthesis of the potent microtubule-stabilizing anticancer agent (-)-laulimalide has been achieved in 27 steps and 2.9% overall yield. Notable features are the use of Jacobsen HDA chemistry for the enantioselective construction of the side chain dihydropyran, a diastereoselective aldol coupling using chiral boron enolate methodology, a Mitsunobu macrolactonization, and a Sharpless AE to introduce the epoxide onto des-epoxy-laulimalide.     

Methyl 2,2-difluoro-2-(fluorosulfonyl)acetate, a difluorocarbene reagent with reactivity comparable to that of trimethylsilyl 2,2-difluoro-2-(fluorosulfonyl)acetate (TFDA)

Under specific high concentration, high temperature conditions, methyl 2,2-difluoro-2-(fluorosulfonyl)acetate (MDFA) has been found to act as a very efficient source of difluorocarbene, exhibiting carbene reactivity characteristics comparable to those exhibited by trimethylsilyl 2,2-difluoro-2-(fluorosulfonyl)acetate (TFDA). For example, in reaction with highly unreactive n-butyl acrylate and using only 2 equiv of MDFA, a yield of 76% of difluorocyclopropane product was obtained after 2 days.     

Dienic sex pheromones : Stereoselective syntheses of (7E,9Z)-7,9-dodecadien-1-yl acetate, (E)-9,11-dodecadien-1-yl acetate,and of (9Z), 11E)-9,11- tetradecadien-1-yl acetate by palladium-catalyzed reactions

Pure (7E,9Z-7, 9-dodecadien-1-yl acetate (1), the sex pheromone of Lobesiabotrana, has been prepared in 21.6% overall yield by a reaction scheme involving; (i) the cross-coupling of (E) - 8 - (2 - tetrahydropyranyloxy) -1 - octenyldisiamylborane with 1 - bromo - 1 - butyne, in the presence of a Pd (O) catalyst and base; (ii) the acetylation of the crude product of this reaction; (iii) the (Z)-stereoselective reduction of the obtained conjugated (E)-enyn-1-yl acetate. (E)-9,11-Dodecadien-1-yl acetate (2), a sex pheromone component of Diparopsiscastanea, has been analogously obtained (in 54.3% overall yield) by cross-coupling of (E) - 10 - (2 - tetrahydropyranyloxy) - 1 - decenyl borane with vinyl bromide, in the presence of a Pd (O) catalyst and base, followed by acetylation of the crude product. Compound 2, which was 87.7% chemically pure, was purified by column chromatography over SiO₂-AgNO₃. Chemically pure (9Z, 11E) - 9,11 - tetradecadien - 1 - yl acetate (3), a sex pheromone component of Spodopteralittoralis, has been prepared (in 30.2% overall yield) by reaction of 10 - (2 - tetrahydropyranyloxy) - 1 - decynylamagnesium bromide with (E)-1-iodo-1-butene, in the presence of a Pd (O) catalyst, followed by acetylation of the crude product and by (Z)-stereoselective reduction of the obtained (E)-enyn-1-yl acetate.The stereoisomeric purity of 1, 2 and 3 has been evaluated by glc analysis on glass capillary columns or by reverse phase hplc analysis.     

4 氨基4′ 氰基联苯的合成

４氨基４′氰基联苯,不仅是制备烷氧基联苯的原料,而且可以制备高正介电各向异性液晶及系列酯类液晶材料．但通常要经过酰化、氧化、酰氯化、氨解、脱水、硝化和还原［１］等多步反应,步骤长、收率低,本文用联苯为原料,经过硝化、碘代、氰代和还原反应合成４氨基４′氰基联苯．反应步骤及时间比原路线减少近一半,而且反应条件温和,收率高．联苯（ＣＰ,上海化学试剂一厂）;Ｎ,Ｎ二甲基甲酰胺（ＡＲ,临平化工试剂厂）;氯仿（ＡＲ,沈阳试剂一厂）;亚硫酸氢钠（ＡＲ,大连辽南化学品厂）;碘酸（ＡＲ,北京化工厂）…     

Preparation and utilization of perillyl acetate

Perillyl acetate is a fragrance compound that was prepared by the reaction of β-pinenoxide with acetic anhydride and using acetic acid as an acid catalyst. Several selected catalysts were tested (homogenous: phosphoric acid, boric acid, acetic acid, and citric acid; heterogeneous: zeolite USY, SSA, and montmorillonite K-10) and the reaction conditions optimized for this reaction. The yield 78.7 % of perillyl acetate was obtained. Mayol (4-isopropylcyclohexylmethanol), a valuable fragrance compound, was further obtained by a two-step synthesis from perillyl acetate. Firstly, perillyl acetate was saponified to perillyl alcohol. The yield of alcohol was 94.4 %. The last step of the entire preparation was the hydrogenation of perillyl alcohol to Mayol. The yield of the desired product of this reaction was 94.6 %.     

Rh(II) acetate catalyzed cyclopropanation of styrenes with enaldiazo esters: diastereoselective synthesis of enal-cyclopropanes

An efficient Rh(II) acetate catalyzed highly diastereoselective cyclopropanation of styrenes with enaldiazo esters has been developed (up to >95:5 dr and 62–82% yield). The reaction is proposed to involve diacceptor electrophilic rhodium enalcarbenoids and constitutes the first direct synthesis of enal-cyclopropanes with an all carbon γ-quaternary stereocenter.     

A chemoenzymatic dynamic kinetic resolution approach to enantiomerically pure (R)- and (S)-duloxetine

The synthesis of (R)-duloxetine is described. Dynamic kinetic resolution of β-hydroxynitrile rac-1 using Candida antarctica lipase B (CALB, N435) and ruthenium catalyst 6 afforded β-cyano acetate (R)-2 in high yield and in excellent enantioselectivity (98% ee). The subsequent synthetic steps were straightforward and (R)-duloxetine was isolated in 37% overall yield over 6 steps. The synthetic route also constitute a formal total synthesis of (S)-duloxetine.     

4-(9-fluorenylmethyloxycarbonyl)phenylhydrazine (FmPH): a new chromophoric reagent for quantitative monitoring of solid-phase aldehydes(1-3)

A direct method for quantifying solid-phase aldehydes has been developed, using a new reagent, 4-(9-fluorenylmethyloxycarbonyl)phenylhydrazine (FmPH). The FmPH reagent was synthesized in three steps (24% overall yield) from commercially available p-hydrazinobenzoic acid. Resin-bound aldehydes reacted quantitatively with FmPH, in the presence of trimethylorthoformate (TMOF) as a dehydrating agent, to form a highly conjugated, immobilized FmPH-hydrazone. Next, mild treatment of the hydrazone with an excess of piperidine-N,N-dimethylformamide (1:1) released the piperidine-dibenzofulvene adduct chromophore (epsilon(301nm) = 7800 M(-1) cm(-1)) from the support. FmPH quantitation of aldehydes proved to be a straightforward, sensitive, and reproducible technique for monitoring resin-bound aldehydes [albeit insufficiently reactive to allow reliable quantification of ketones]. The FmPH aldehyde assay is applicable to a range of solid supports, as demonstrated specifically for poly(ethylene glycol)-polystyrene (PEG-PS), aminomethylpolystyrene (AMP), and cross-linked ethoxylate acrylate resin (CLEAR).     

Synthetic transformation of ptychantin into forskolin and 1,9-dideoxyforskolin

Forskolin (1), a highly oxygenated labdane diterpenoid and an activator of adenylate cyclase, has been synthesized in 12 steps and 12% overall yield from ptychantin A (4), which has been isolated from liverwort Ptychanthus striatus in good yield. The 1alpha-hydroxy group was furnished by stereoselective reduction of the corresponding carbonyl group by sodium in t-BuOH. The 9alpha-hydroxy group was introduced stereoselectively by epoxidation of delta(9.11)-enolether. 1,9-Dideoxyforskolin (2), an inhibitor of glucose transporter, has been synthesized in 8 steps and 37% overall yield. The hydroxy group at C-1 was removed by solid-state thicarbonylimidazolation and subsequent radical cleavage.     

Asymmetric total synthesis of (+)-gabosine C and (+)-4-epi-gabosine J using acetate migration and RCM reaction

A concise, unified and stereoselective total synthesis of (+)-gabosine C and (+)-4-epi-gabosine J from a common polyhydroxylated cyclohexenol intermediate which was synthesized from readily available D-ribose has been described. The synthetic avenue includes stereoselective Grignard reaction, silyl ether deprotection followed by acetate migration, RCM reaction, oxidative diol cleavage, hydroxymethylation and oxidative rearrangement as key steps.     

Synthesis of terpinyl acetate using octadecylamine ethoxylate ionic liquids as catalysts

Terpinyl acetate, an important natural flavor, can be synthesized by esterification of α-pinene with acetic acid under acidic conditions. In this work, seven acidic ionic liquids were first synthesized, using octadecylamine ethoxylates (AC 1810, AC 1815, AC 1820, and AC 1830) as the cations, and characterized by FT-IR, ¹H NMR, and ¹³C NMR spectroscopy. The ionic liquids were then used as catalysts in the synthesis of terpinyl acetate. The effect of preparation conditions on catalyst performance was examined. It was found that the acidic ionic liquid 1-(3-sulfonic acid)propyl-3-poly(ethylene glycol) octadecylamine polyoxyethylene ether tetrafluoroborate ([PAC1815]⁺[BF₄]^?) was an excellent catalyst for synthesis of terpinyl acetate. The effects of the conditions used for preparation of terpinyl acetate were examined in detail, and the optimum preparation conditions were obtained. Under the optimum conditions, the yield of terpinyl acetate reached 35.70 %. When the catalyst was reused for the 5th time, the yield of terpinyl acetate was still 32.00 %. The results showed that effective separation and recycling of catalyst could contribute to developing a new strategy for synthesis of terpinyl acetate.     

A six-step asymmetric synthesis of (+)-hyperaspine

[reaction: see text] The ladybird alkaloid, (+)-hyperaspine, has been synthesized in a concise and highly stereoselective manner. The total synthesis was accomplished in six steps and 21% overall yield.     

乙酸异丙酯的合成

以乙酸和异丙醇为原料,硫酸氢钠为催化剂,合成了乙酸异丙酯;考察了反应时间、酸醇比、催化剂用量、带水剂用量对酯化率的影响,确定了最佳酯化反应条件:反应时间60min,酸醇的物质的量的比1∶0.8,催化剂用量0.8g,带水剂用量8mL.在最佳反应条件下,酯化率最高可达84.3%.     

Synthesis of mimosamycin

Mimosamycin (1) was synthesized in eight steps with an overall yield of 13% from 2-methoxy-3-methyl-1,4-benzoquinone by regioselective introduction of a chloromethyl group at C-6 and a methoxycarbonylmethyl group at C-5 and subsequent reaction of the intermediate methyl (o-(chloromethyl)phenyl)acetate derivative 16 with methylamine. Oxidation of the 5,7,8-trimethoxy-2,6-dimethyl-1, 4-dihydroisoquinoline-3(2H)-one 17 thus obtained, using cerium(IV) ammonium nitrate as a selective oxidizing agent, gave mimosamycin (1) in good overall yield.