Nature of anion-templated π(+)-π(+) interactions

Interaction between positively charged aromatic groups (π(+)-π(+)) is characterized by anti-parallel, displaced-stacked structures in the presence of counteranions. Binding energies of pyridinium, N-methylpyridinium and N-methylimidazolium dimers are much larger than that of benzene-pyridine (π-π) and pyridinium-benzene (π(+)-π). Stabilization is attributed to attractive electrostatic interaction with significant dispersion contribution.     

Asymmetric total syntheses of (+)-goniopypyrone and (+)-9-deoxygoniopypyrone

Asymmetric total syntheses of (+)-goniopypyrone (1) and (+)-deoxygoniopypyrone (2) from methyl cinnamate (7) via (DHQ)2-PHAL-OsO4 catalyzed asymmetric dihydroxylation and highly stereoselective 2-furylcopper addition in eight steps and eleven steps with overall yield of 20% and 13%,respectively,are described.     

Total syntheses of macrosphelides (+)-A, (−)-A and (+)-E

Total syntheses of (+)-macrosphelide A 1 (18.5% overall yield in 11 steps) and (+)-macrosphelide E 2 (23.9% overall yield in 11 steps) have been achieved via the chemoenzymatic reaction product (4R,5S)-4-benzyloxy-5-hydroxy-2(E)-hexenoate 4. The enantiomer (−)-A (1) (14.2% overall yield in 11 steps) of (+)-1 was also synthesized from the chemoenzymatic reaction product (4S,5R)-4-benzyloxy-5-hydroxy-2(E)-hexenoate 4.     

Total Synthesis of (+)Villosol

Villosol,aniridoid,wasisolatedin1985fromChineseherbmedicineP8triniaviIios8'itSstrUctUrewasproPOsedas(A)ll].lnourpreviouspaperi2],wehavereP0rtedthesynthesisofthesubstance(l)A,andf0undittobesPectraIlynonidenticalwiththenaturalisolate.Later,throughX-rayanalysisl'],wehaveconfirmedthatthesmictUreofvillosolwasB.Herein,wedisclosethefirstStereoselectivetotalsynthesisof(+)B.Oursynthesisbeganwithcompound2,whichwasreadilypreparedandresolvedtoitSoPticalformsinlargescalebyAnownmethodI41.After(l)2w…     

Stereoselective Synthesis of (+)-Boronolide

(+)-Boronolide (1) and its deacetylated products have attracted much attention of synthetic chemists due to their diverse biological properties as well as their structural complexities.[1] Many of these reported synthesis involved dehydrogenation of δ-lactone by using benzeneseleninic anhydride or ring-closing olefin metathesis (RCM) to introduce the requisite α,β-unsaturated δ-lactone in boronolide. Here, we report the synthesis of boronolide with diastereoselective propargylation of α-hydroxy aldehyde as the key step and D-gluconolactone as the starting material.     

Synthesis of (+)-altholactone, (+)-7-epi-altholactone, (−)-etharvensin,and (+)-alumheptolide-A using Pd-catalyzed carbonylation

Syntheses of (+)-altholactone isolated from Goniothalamus giganteus and its C-7 epimer (+)-7-epi-altholactone, (?)-etharvensin and (+)-alumheptolide-A were achieved. The lactone ring of these compounds was constructed using Pd-catalyzed carbonylation.     

A SIMPLE SYNTHESIS OF (+)-ACETYLGONIOTRIOL

ＡＳＩＭＰＬＥＳＹＮＴＨＥＳＩＳＯＦ（＋）－ＡＣＥＴＹＬＧＯＮＩＯＴＲＩＯＬ￥ＺｈｉＣａｉＹＡＮＧａｎｄＷｅｉＳｈａｇＺＨＯＵ￣＊（ＳｈａｎｇｈａｉＩｎｓｔｉｔｕｔｅｏｆＯｒｇａｎｉｃＣｈｅｍｉｓｔｒｙ，ＣｈｉｎｅｓｅＡｃａｄｅｍｙｏｆＳｃｉｅｎｃｅ...     

(+)-生物素全合成研究新进展

(+)-生物素是维生素B家族中的一员,自发现以来对其全合成的报道层出不穷.在最近十几年中,数十条新的合成路线和改进方法陆续报道.(+)-生物素全合成策略主要分为两类:对映选择性合成和立体专一性合成.前一策略中,通过各种反应方法对经典的Hoffmann-La-Roche-硫内酯法进行改进和完善,其中不对称催化合成的方法已成功应用于工业化生产;在后一策略中,以L-半胱氨酸为起始原料的合成途径得到了较大发展,正越来越具有工业意义.     

Expedient enantioselective synthesis of the δ4-oxocene cores of (+)-laurencin and (+)-prelaureatin (‡)

An expedient enantioselective synthesis of the Δ(4)-oxocene cores present in (+)-laurencin and (+)-prelaureatin was accomplished in eight steps via a novel one-pot regio- and stereoselective ring cyclization-fragmentation-expansion cascade from the tetrahydrofuran precursors which were prepared by stereocontrolled cyclization from vinylsilanes. This process is highlighted by an intramolecular oxo-carbenoid insertion and a β-silyl fragmentation sequence.     

Terpenes in organic synthesis 13. Synthesis of s-(+)-methoprene from (+)-β-citronellene

S-(+)-Methoprene (I) was synthesized from (+)--citronellene (III) with an optical purity of about 50%. The optical purity of the key intermediate, S-(–)-7-methoxy-3,7-dimethyl-1-octanol (IV), can be increased by fractional crystallization of the optically active acid phthalate salt (VI) followed by hydrolytic regeneration of alcohol (IV). The yield of (I) at the final synthetic stage can be increased by use of interphase catalysis. S-(+)-Methoprene has a higher morphogenetic activity than the racemic form.For previous communication, see [1].Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 4, pp. 842–846, April, 1991.     

(+)-氧化樟脑的合成研究

(+)-氧化樟脑是(+)-樟脑在体内的代谢产物,临床上主要用于治疗呼吸和循环衰竭.目前(+)-氧化樟脑的合成方法存在反应时间长、反应条件剧烈、收率低、污染严重等问题.本研究以天然(+)-樟脑为起始原料,经过溴化、还原、酯化、水解和氧化反应合成了目标产物(+)-氧化樟脑.各步中间体及目标产物经1H NMR、IR和GC-MS验证了结构,并且运用单晶X射线衍射确定了关键中间体3,9-二溴樟脑的绝对构型.这条路线反应条件温和,操作简便,避免了使用重金属作为氧化剂和还原剂,是一条环境友好的合成路线.     

TOTAL SYNTHESIS OF(+)-7-EPI-GONIDFUFURONE

First total synthesis of natural styryl-furone,(+)-7-epi-goniofufurone 1,from D-glycero-D-gulo-heptono-γ-lactone in eight steps(13%overall)is described.The absolute stereochemistry of 1 is confirmed.     

An approach towards the total synthesis of (+)-epiquinamide and (+)-α-conhydrine from Garner aldehyde

A short and stereoselective route for the synthesis of 1-hydroxyquinolizidine, an advanced synthetic intermediate for the total synthesis of (+)-epiquinamide is presented. The key synthetic steps involve diastereoselective nucleophilic addition on l-serine derived Garner aldehyde and acid mediated (PTSA) ring closing metathesis. The methodology is also elaborated successfully for the total synthesis of (+)-α-conhydrine, an important piperidine alkaloid.     

L(+)-乳酸提取纯化新工艺

发酵制备L(+)-乳酸过程中,发酵醪液分离提纯的时间和成本占到整个生产过程的一半以上,大大限制了乳酸生产工业的发展.针对此种情况,需探索出低成本高效率的分离提纯精制L(+)-乳酸的新工艺,以提高产品收率和纯度.本工艺过程:发酵醪液微波灭菌、高速离心、活性碳除色、膜过滤除蛋白质、柱分离、柱精制、真空浓缩得成品.生产过程不产生硫酸钙废弃物,减少对环境的污染,提取率由原来50%提高到71%以上.     

The Formal Stereoselective Synthesis of(+)-Preussin

(+)-Preussin(l).apolysubstitutedpyrrolidinealkaloidisolatedfromthendcroorganismsPrc~SP.andAsPedusocboccllsinthelatel98o'sl'],isofconsiderableimportanceduetoitsbio-activib'asgro\vthi11llibitorofthebacte1ja,thedall,andfilan1entousfungi,includingTI7toop~,ncntaandM~mcanisMoreover,(+)-preussinanditsacetateestershowabroaderspectrUmofantlifungalachvity'againdbothfilamentousfungiandyeaStsthanitSstrUcturallyrelatedanhbioticanisomycin(2).Consequenhy,muchattenhonhasbeendevotedtotheSynthesisl']of(+)-…     

(+)-菊花烯酮的Baeyer-Villiger反应

Baeyer-Villiger反应是酮在过氧酸氧化下形成酯的反应,是有机反应中合成酯的主要方法,这一反应可应用在环酮扩环形成含氧杂环内酯的反应上．由于反应是立体控制的,已广泛应用于天然产物,例如：抗生素、类固醇和信息素中间体的合成,某些用其它方法难以合成的羟基酸可由内酯水解得到。     

(+)-柳杉酚的简便合成

报道了两种(+)-柳杉酚(6)的简便合成路线。路线1:脱氢枞胺(1)经脱氨还原,12-位Friedele-Crafts乙酰化,Baeyer-Villiger氧化,7-位氧化和水解5步反应合成了6,总产率18.6%。路线2:1经脱氨还原和7-位氧化反应制得7-氧代脱氢松香烷(7);7与过氧化邻苯二甲酰反应,然后水解合成了6,总产率22.0%。6的结构经1H NMR,IR,TOF-MS和元素分析确证。     

Vibrational energies of LiH2(+) and LiD2(+) in the Ã1Σ+ electronic state

In connection with the recent study of the ground electronic state of the LiH2(+) molecular ion (Kraemer, W. P.; Spirko, V. Chem. Phys. 2006, 330, 190), the adiabatic three-dimensional double-minimum potential enery surface of the first excited electronic state was evaluated, including its two lowest atom-diatom dissociation channels as well as the three-atom complete fragmentation asymptote. Applying the Sutcliffe-Tennyson Hamiltonian for triatomic molecules, the levels of all bound vibrational states and the levels of the states localized in the two energy minimum regions were separately determined. The validity of statistical methods such as the density of states approach and the nearest-neighbor level spacing distribution (NNSD) was tested for the light LiH2(+) ion. Special effort was put into investigating possible effects of a tunnelling motion across the proton-transfer barrier on the vibrational level pattern using the NNSD approach.     

Total syntheses of (+)-polygalolide a and (+)-polygalolide b: elucidation of the absolute stereochemistry and biogenetic implications

The total syntheses of (+)-polygalolide?A and (+)-polygalolide?B have been completed by using a carbonyl ylide cycloaddition strategy. Three of the four stereocenters, including two consecutive tetrasubstituted carbon atoms at C2 and C8, were incorporated through internal asymmetric induction from the stereocenter at C7 by a [Rh(2) (OAc)(4)]-catalyzed carbonyl ylide formation/intramolecular 1,3-dipolar cycloaddition sequence. The arylmethylidene moiety of these natural products was successfully installed by a Mukaiyama aldol-type reaction of a silyl enol ether with a dimethyl acetal, followed by elimination under basic conditions. We have also developed an alternative approach to the carbonyl ylide precursor based on a hetero-Michael reaction. This approach requires 18 steps, and the natural products were obtained in 9.8 and 9.3?% overall yields. Comparison of specific rotations of the synthetic materials and natural products suggests that polygalolides are biosynthesized in nearly racemic forms through a [5+2] cycloaddition between a fructose-derived oxypyrylium zwitterion with an isoprene derivative.