摘要:

A Simple Route to 3‐Amino‐nocardicinic AcidStarting from nocardicin A (1), a novel and efficient procedure for the preparation of 3‐amino‐nocardicinic acid (4) and its protected derivatives6and8–11is

ISSN:0018-019X    

DOI:10.1002/hlca.19800630202

出版商:WILEY‐VCH Verlag GmbH    

年代:1980

数据来源: WILEY

摘要:

Structural Modification on Partially Silylated Carbohydrates by Means of Triphenylphosphine/Diethyl AzodicarboxylateReaction of methyl 2, 6‐bis‐O‐(t‐butyldimethylsilyl)‐β‐D‐glucopyranoside (1a) with triphenylphosphine (TPP)/diethyl azodicarboxylate (DEAD) and Ph3P · HBr or methyl iodide yields methyl 3‐bromo‐2, 6‐bis‐O‐(t‐butyldimethylsilyl)‐3‐deoxy‐β‐D‐allopyranoside (3a) and the corresponding 3‐deoxy‐3‐iodo‐alloside3c(Scheme 1). By a similar way methyl 2, 6‐bis‐O‐(t‐butyldimethylsilyl)‐α‐D‐glucopyranoside (2a) can be converted to the 4‐bromo‐4‐deoxy‐galactoside4aand the 4‐deoxy‐4‐iodo‐galactoside4b. In the absence of an external nucleophile the sugar derivatives1aand2areact with TPP/DEAD to form the 3,4‐anhydro‐α‐ or ‐β‐D‐galactosides5and6a, respectively, while methyl 4, 6‐bis‐O‐(t‐butyldimethylsilyl)‐β‐D‐glucopyranoside (1b) yields methyl 2,3‐anhydro‐4, 6‐bis‐O‐(t‐butyldimethylsilyl)‐β‐D‐allopyranoside (7a, s.Scheme 2). Even the monosilylated sugar methyl 6‐O‐(t‐butyldimethylsilyl)‐α‐D‐glucopyranoside (2b) can be transformed to methyl 2,3‐anhydro‐6‐O‐(t‐butyldimethylsilyl)‐β‐D‐allopyranoside (8; 56%) and 3,4‐anhydro‐α‐D‐alloside9(23%, s.Scheme 3). Reaction of1cwith TPP/DEAD/HN3leads to methyl 3‐azido‐6‐O‐(t‐butyldimethylsilyl)‐3‐deoxy‐β‐D‐allopyranoside (10). The epoxides7and8were converted with NaN3/NH4Cl to the 2‐azido‐2‐deoxy‐altrosides11and13, respectively, and the 3‐azido‐3‐deoxy‐glucosides12and14, respectively (Scheme 4and5). Reaction of7and8with TPP/DEAD/HN3orp‐nitrobenzoic acid afforded methyl 2,3‐anhydro‐4‐azido‐6‐O‐(t‐butyldimethylsilyl)‐4‐deoxy‐α‐ and ‐β‐D‐gulopyranoside (15and17), respectively, or methyl 2,3‐anhydro‐6‐O‐(t‐butyldimethylsilyl)‐4‐O‐(p‐nitrobenzoyl)‐α‐ and ‐β‐D‐gulopyranoside (16and18), respectively, without any opening of the oxirane ring (s.Scheme 6). ‐ The 2‐acetamido‐2‐deoxy‐glucosides19aand20areact with TPP/DEAD alone to form the corresponding methyl 2‐acetamido‐3,4‐anhydro‐6‐O‐(t‐butyldimethylsilyl)‐2‐deoxy‐galactopyranosides (21and22) in a yield of 80 and 85%, respectively (Scheme 7). With TPP/DEAD/HN320ais transformed to methyl 2‐acetamido‐3‐azido‐6‐O‐(t‐butyldimethylsilyl)‐2,3‐didesoxy‐β‐D‐allopyranoside (25,Scheme 8). By this way methyl 2‐acetamido‐3,6‐bis‐O‐(t‐butyldimethylsilyl)‐α‐D‐glucopyranoside (19b) yields methyl 2‐acetamido‐4‐azido‐3,6‐bis‐O‐(t‐butyldimethylsilyl)‐2,4‐dideoxy‐α‐D‐galactopyranoside (23; 16%) and the isomerized produ

ISSN:0018-019X    

DOI:10.1002/hlca.19800630203

出版商:WILEY‐VCH Verlag GmbH    

年代:1980

数据来源: WILEY

摘要:

Isomerization of Protonated Aldehyde and Ketone Ions in the Mass‐Spectrography Before the Loss of WaterIn mass spectrometry, protonated aldehyde and ketone ions isomerize before the loss of a molecule of water. In order to specify this process, the spectra of deuterium labelled protonated aldehydes and ketones have been compared to the spectra of the corresponding isomer ion

ISSN:0018-019X    

DOI:10.1002/hlca.19800630204

出版商:WILEY‐VCH Verlag GmbH    

年代:1980

数据来源: WILEY

摘要:

A Novel Example of Reversible Ring Opening: The Epimerization at C(3) of Sugar 3‐Hydroxy‐Δ1‐pyrazolinesReaction of1(either geometrical isomer) with hydrazine followed byin situAg2O oxidation led to two pairs of interconverting isomers4 ⇄ 5and6 ⇄ 7. By the same treatment, (Z)‐10and (or) (E)‐10gave the pair11 ⇄ 12. Acetylation of4 ⇄ 5led to a non interconverting mixture of8and9. This fact, and the lack of incorporation of18O when the epimerization took place in the presence of H218O indicated that the most probable mechanism consisted in a reversible ring opening (D ⇄ E ⇄ F). The kinetic parameters of these reactions are given and structural assignments proposed

ISSN:0018-019X    

DOI:10.1002/hlca.19800630205

出版商:WILEY‐VCH Verlag GmbH    

年代:1980

数据来源: WILEY

摘要:

AbstractThe synthesis and conformational analysis of (3′R)‐3‐hydroxyleurosidine (5), (3′S)‐3‐hydroxyleurosidine (10), (3′S)‐3‐acetoxy‐4′‐deoxyleurosidine (15), (3′R)‐3‐acetoxy‐4′‐deoxyleurosidine (23), (3′R)‐3‐acetoxy‐4′‐deoxyvinblastine (16), (3′S

ISSN:0018-019X    

DOI:10.1002/hlca.19800630206

出版商:WILEY‐VCH Verlag GmbH    

年代:1980

数据来源: WILEY

摘要:

AbstractWater‐insoluble oligomers were synthesized fromL‐methionine ethyl ester with papain as the catalyst.L‐Oligomethionine was obtained in yields of 50% when synthesis was carried out in highly concentrated citrate buffer at pH 5.5. Yields of up to 85% were obtained when the enzymatic synthesis proceeded in distilled water at pH 6.5, the pH being strictly maintained. The insoluble polymer was converted to highly water‐soluble sulfoxide and sulfone derivatives, which consist mainly of an octamer with low amounts of heptamer or hexamer. Most of the carboxyl terminals still contained the ethyl ester group, only a minor part being present in the free acid form. The potential of the enzymatic approach for the synthesis of optically pure and monodisperse oligomers of α‐amino acids is

ISSN:0018-019X    

DOI:10.1002/hlca.19800630207

出版商:WILEY‐VCH Verlag GmbH    

年代:1980

数据来源: WILEY

摘要:

On the Synthesis of Sulfonated Derivatives of 2,3‐Dimethylaniline and 3,4‐DimethylanilineBaking the hydrogensulfate salt of 2,3‐dimethylaniline (1) or of 3,4‐dimethylaniline (2) led to 4‐amino‐2,3‐dimethylbenzenesulfonic acid (4) and 2‐amino‐4,5‐dimethylbenzenesulfonic acid (5), respectively(Scheme 1). The sulfonic acid5was also obtained by treatment of2with sulfuric acid or by reaction of2with amidosulfuric acid. 3‐Amino‐4,5‐dimethylbenzenesulfonic acid (3) and 5‐Amino‐2,3‐dimethylbenzenesulfonic acid (6) were prepared by sulfonation of 1,2‐dimethyl‐3‐nitrobenzene (9) to 3,4‐dimethyl‐5‐nitrobenzenesulfonic acid (11) and of 1,2‐dimethyl‐4‐nitrobenzene (10) to 2,3‐dimethyl‐5‐nitrobenzenesulfonic acid (12), respectively, with subsequentBéchampreduction(Scheme 1). Preparations of 2‐amino‐3,4‐dimethylbenzenesulfonic acid (7) and of 6‐amino‐2,3‐dimethylbenzenesulfonic acid (8) were achieved by the sulfur dioxide treatment of the diazonium chlorides derived from 3,4‐dimethyl‐2‐nitroaniline (24) and from 2,3‐dimethyl‐6‐nitroaniline (31) to 3,4‐dimethyl‐2‐nitrobenzenesulfonyl chloride (29) and 2,3‐dimethyl‐6‐nitrobenzenesulfonyl chloride (32), respectively, followed by hydrolysis to 3,4‐dimethyl‐2‐nitrobenzenesulfonic acid (30) and 2,3‐dimethyl‐6‐nitrobenzenesulfonic acid (33), and final reduction(Scheme 3). Compound7was also synthesized by reaction of 4‐chloro‐2,3‐dimethylaniline (23) with amidosulfuric acid to 2‐amino‐5‐chloro‐3,4‐dimethylbenzenesulfonic acid (20) and subsequent hydrogenolysis(Scheme 2). 4′‐Bromo‐2′, 3′‐dimethyl‐acetanilide (13) and 4′‐chloro‐2′, 3′‐dimethyl‐acetanilide (14) on treatment with oleum yielded 5‐acetylamino‐2‐bromo‐3,4‐dimethylbenzenesulfonic acid (17) and 5‐acetylamino‐2‐chloro‐3,4‐dimethylbenzenesulfonic acid (18), respectively. Their structures were proven by

ISSN:0018-019X    

DOI:10.1002/hlca.19800630208

出版商:WILEY‐VCH Verlag GmbH    

年代:1980

数据来源: WILEY

摘要:

On the Pathway of the Catalytic Reduction of 7‐MethylpterinThe catalytic hydrogenation of 7‐methylpterin (VII) in a neutral solution occurs first by the reduction of the 7,8‐double bond (thermodynamically‐controlled reaction) followed by the reduction of the 5,6‐double bond. On the contrary, in an acidic medium like CF3COOH, the 5,6‐double bond is reduced first (kinetically‐controlled reaction). The dihydro‐intermediate then undergoes a [1,2]‐H‐rearrangement leading to the formation of the thermodynamically more stable 7‐methyl‐7,8‐dihydropterin (XV) which on further reduction gives 7‐methyl‐5,6,7,8‐tetrahydropterin (VIII). The catalytic reduction of 7‐methyl‐7,8‐dihydropterin (XV) with deuterium gives stereoselectively a sole product with

ISSN:0018-019X    

DOI:10.1002/hlca.19800630209

出版商:WILEY‐VCH Verlag GmbH    

年代:1980

数据来源: WILEY

摘要:

AbstractThe reaction of a cinnamoyl chloride with excess trimethyl phosphite gives a substituted 1,5‐hexadiene, in which C,C‐bond formation has taken place between the β‐C‐atoms of the two α, β‐unsaturated carbo

ISSN:0018-019X    

DOI:10.1002/hlca.19800630210

出版商:WILEY‐VCH Verlag GmbH    

年代:1980

数据来源: WILEY

摘要:

Revision der Struktur von «Epoxycolchicin»Die für natürliches «Epoxycolchicin» vorgeschlagene Struktur2muss aufgrund einer Kristall‐Röntgenstrukturanalyse zu derjenigen des cyclischen Acetals3abgeändert werden. Es wird vorgeschlagen, den Namen «Epoxycolchicin» aus der Literatur zu streichen, da er irre

ISSN:0018-019X    

DOI:10.1002/hlca.19800630211

出版商:WILEY‐VCH Verlag GmbH    

年代:1980

数据来源: WILEY