摘要:

AbstractA variety of alcohols of the 1‐oxycyclopropyl structure, prapared mostly from α‐alkoxy‐α,β‐unsaturated ketnnes and esters by way of reductinn andSimmons‐Smithreaction of the resultant α‐alkoxyallyl alcohols, are shown to rearrange into cyclobutanones on acid treatment

ISSN:0018-019X    

DOI:10.1002/hlca.19770600102

出版商:WILEY‐VCH Verlag GmbH    

年代:1977

数据来源: WILEY

摘要:

Kinetics of very fast Methylmercury‐Transfer Reactions between Pyridine‐containing Chelating Ligands and the Hydroxide IonThe kinetics of the reactions between methylmercury hydroxide and bipyridine, terpyridine, phenanthroline and pyridine‐2‐azo‐4‐dimethylaniline have been studied by means of the temperature jump relaxation method. These bi‐ and tridentate ligands form methylmercury chelates. Their formation is faster than the formation of the pyridine complex. The chelate complexes show an unusually high reactivity. Their reaction rates with hydroxide ions reach almost the diffusion con

ISSN:0018-019X    

DOI:10.1002/hlca.19770600103

出版商:WILEY‐VCH Verlag GmbH    

年代:1977

数据来源: WILEY

摘要:

Synthese of sulfonated derivatives of 2‐amino‐p‐xyleneSulfonation of 2‐amino‐p‐xylene(2)gave 2‐amino‐p‐xylene‐5‐sulfonic acid(1). The 2‐amino‐p‐xylene‐6‐sulfonic acid(3)was preparedviathree routes: (1) sulfonation of 2‐amino‐5‐chloro‐p‐xylene(19)to 5‐amino‐2‐chloro‐p‐xylene‐3‐sulfonic acid(20)followed by hydrogenolysis; (2) sulfur dioxide treatment of the diazonium salt derived from 2‐amino‐6‐nitro‐p‐xylene(21)to 2‐nitro‐p‐xylene‐6‐sulfonyl chloride(11)followed by hydrolysis to 2‐nitro‐p‐xylene‐6‐sulfonic acid(4)andBéchampreduction; (3)Béchampreduction of 2‐chloro‐3‐nitro‐p‐xylene‐5‐sulfonic acid(13)to 3‐amino‐2‐chloro‐p‐xylene‐5‐sulfonic acid(16)and subsequent hydrogenolysis. Catalytic reduction of13in aqueous sodium carbonate solution gave mixtures of3and16. 2‐Amino‐p‐xylene‐3‐sulfonic acid(27)was synthesizedviatwo routes: (1) reaction of19with sulfamic acid to 2‐amino‐5‐chloro‐p‐xylene‐3‐sulfonic acid(26)followed by hydrogenolysis; (2) sulfur dioxide treatment of the diazonium salt derived from 2

ISSN:0018-019X    

DOI:10.1002/hlca.19770600104

出版商:WILEY‐VCH Verlag GmbH    

年代:1977

数据来源: WILEY

摘要:

Total synthesis of human insulin. IV. Description of the final steps.Recently a preliminary account was given of a new synthetic pathway leading to human insulin. In the present report the last steps of this synthesis –i.e.as from the unsymmetrical cystine derivative I – are described in detail. I contains the sequences A(14–21) and B(17–30), linked by the disulfide bridge A20‐B19. These last steps are: (1) selective removal by pH‐controlled acidolysis in trifluoroethanol ofN(α)‐Trt from leucine B17, (2) completion of the B‐chain by coupling with the fragment B(1–16), (3) selective removal by trifluoroethanol ofN(α)‐Bpoc at tyrosine A14, (4) completion of the A‐chain by coupling with the cyclic fragment A(1–13), (5) removal of the acid labile protecting groups, and (6) formation of the disulfide bond A7–B7 from the twoS‐acetamido‐protected cysteine residues by treatment with iodine.As judged by the composition of the reaction mixture the closure of the 85‐membered ring proceeds with a cyclization yield of over 70%. From the last step in the synthesis two products were obtained after extensive purification by counter‐current distribution: pure human insulin in a yield of 50% and its [D‐tyrosine B16]Isomer in a yield of 25%. Although the partial racemization of tyrosine B16 occurred during coupling with sequence B(1–16), the [D‐tyrosine B 16]‐stereoisomer could only be separated at the endproduct stage.The available evidence indicates that the ease of formation of the disulfide bond A7–B7 does not depend on the precursor molecul

ISSN:0018-019X    

DOI:10.1002/hlca.19770600105

出版商:WILEY‐VCH Verlag GmbH    

年代:1977

数据来源: WILEY

摘要:

AbstractIrradiation of pale yellow 5‐methyl‐1, 4‐naphthoquinone (1,Scheme 1) yields the blue photoenol 4‐hydroxy‐5‐methylidene‐1(5H)‐naphthalenone(2)which is stable at 77 K. At room temperature the enol retautomerizes to starting material, the reaction rate being strongly dependent on the hydrogen‐bond‐acceptor basicity of the solvent. The enol is trapped in the presence of acid by protonation at the remaining carbonyl oxygen atom and subsequent electrophilic reaction of the exocylc

ISSN:0018-019X    

DOI:10.1002/hlca.19770600106

出版商:WILEY‐VCH Verlag GmbH    

年代:1977

数据来源: WILEY

摘要:

Asymmetric synthesis ofL‐γ‐carboxyglutamic acid derivativesA modifiedStreckersynthesis according toPatel&Worsleywas used to prepare γ,γ′‐di‐t‐butylL(−)‐N‐phthaloyl‐γ‐carboxyglutamate with almost 100% optical purity and an overall yield of about 10% relative to di‐t‐butyl malonate, or 20% relative to (−)

ISSN:0018-019X    

DOI:10.1002/hlca.19770600107

出版商:WILEY‐VCH Verlag GmbH    

年代:1977

数据来源: WILEY

摘要:

Abstractdl‐Pumiliotoxin‐C(4)was synthesized in a practical manner fromtrans‐4‐hexenal(9). The key step14→15(Scheme 3) involves an intramolecularDiels‐Alderreaction giving mainly thecis‐fused indanols15a, which were converted to thecis‐fused ketone16. AfterBeckmann‐rearrangement of16the octahydroquinolinone7was transformed to the lactim‐ether23. (Scheme 7). Reaction of23with propylmagnesium bromide followed by hydrogenation furnisheddl‐4in a highly st

ISSN:0018-019X    

DOI:10.1002/hlca.19770600108

出版商:WILEY‐VCH Verlag GmbH    

年代:1977

数据来源: WILEY

摘要:

AbstractPreparation of the title compounds11,12and13is described. Preliminary kinetic results indicate that the hydroxyl substituents in11and12have a very small retardation effect on theDiels‐Alderreactivity of 2,3‐dimethylidene‐norbornane. The keto group in13exerts a larger retardation effect, although it is much smaller than the retardation effect introduced by anexo‐5,6‐epoxide ring in 2,3‐dimethylidene

ISSN:0018-019X    

DOI:10.1002/hlca.19770600109

出版商:WILEY‐VCH Verlag GmbH    

年代:1977

数据来源: WILEY

摘要:

AbstractA simple synthesis of a series of bicyclo[m.n.0]‐1‐alkenes (m, n = 3,4,5) from 2‐oxocycloalkanecarboxylates by the intramolecularWittigreaction is reported (see p. 70–72). The spectral properties (IR.,1H‐NMR. and13C‐NMR.) of these annulated trisubstituted olefins ar

ISSN:0018-019X    

DOI:10.1002/hlca.19770600110

出版商:WILEY‐VCH Verlag GmbH    

年代:1977

数据来源: WILEY

摘要:

AbstractA convenient synthesis of the strained methylene‐bridgedtrans‐cyclooctenes bicyclo[3.3.1]‐1 (2)‐nonene(1), bicyclo[4.2.1]‐1(8)‐nonene(2), and bicyclo[4.2.1]‐1(2)‐nonene(3)by the intramolecularWittigreaction is described (seeSchemes 1–4). The (3‐oxocycloalkyl)alkyl‐phosphonium bromides20,27and38undergoing cyclization to the bridgehead olefins are formed by simple reaction sequences. The spectral properties (IR.,1H‐NMR.,13C‐NMR., and UV.) of the olefins are discussed wi

ISSN:0018-019X    

DOI:10.1002/hlca.19770600111

出版商:WILEY‐VCH Verlag GmbH    

年代:1977

数据来源: WILEY