摘要:

During the past decade a new leaving group, the trifluoromethanesufonate (triflate), has been used increasingly in displacement reactions in carbohydrate chemistry*. The importance of this group has become progressively more apparent to the synthetic carbohydrate chemist as the examples of triflate displacement have increased. The number of applications of this reaction now has reached a sufficient magnitude that it seems appropriate to review what has been accomplished.

ISSN:0732-8303    

DOI:10.1080/07328308408057896

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

Hydrazinolyses of hexa-0-benzoyl-tetra-N-benzyloxycarbonyl-andN-ethoxycarbonylkanamycin A were performed and found to be sufficiently regioselective to give the corresponding 2′-hydroxyl derivatives in good yields under controlled conditions. The products were converted into the corresponding 2′-triflates, which were then subjected to nucleophilic substitution reactions with sodium benzenethioxide, sodium benzoate, and sodium azide to give the correspondingd-mannopyranosyl derivatives in good yields. Deprotection of the phenylthio (10) and azido (12) derivatives, and hydrogenolysis, gave 2′-deoxykankmycin A and 2′-epi-kanamycin B, respectively. Moreover, deprotection of the benzoyl compound11gave 2′-epi-kanamycin A.

ISSN:0732-8303    

DOI:10.1080/07328308408057897

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

Direct 1-O-methylation of 1-O-metalated 2,3,4,6-tetra-O-benzyl-d-glucose (1) with methyl trifluoromethanesulfonate (3a) as a strong alkylating agent led to the methyl gluco-pyranosides4awith the α/β anomer ratios varying from 4:1 to 1:11 depending on solvent and temperature. With the less electrophilic trifluoromethanesulfonates ofd-glucose3band3c, ofd-ribose3d, andd-glycerol (3e) as alkylating agents,1gave the β-disaccharides and β-glycosides4b-β 4e-β, exclusively. Product formation is discussed in terms of the various nucleophilicities of the starting materials and in terms of different internal complexation. Introduction of the sterically demanding (p-methoxyphenyl)diphenyl-methyl protecting group in 6-O-position of 2,3,4-tri-O-ben-zyl-D-glucose to form8and subsequent 1-O-metalation and reaction with trifluoromethanesulfonate3cgave the α-con-nected isomaltoside9C-α. However, from 1-O-metalated8and the trifluoromethanesulfonates of glycerol3eand3funder identical reaction conditions, only the β-connected glycosides9e-β and9f-β, respectively, were obtained. Structures were assigned by1H NMR and by deprotection to known compounds.

ISSN:0732-8303    

DOI:10.1080/07328308408057898

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

1,2:3,4-Di-O-isopropylidene-6-O-nitro-a-d-galacto-pyranose (13), 1,2:5,6-di-O-isopropylidene-3-O-nitro-ct-d-glucofuranose (14), 2,3:4,5-di-O-isopropylidene-l-O-nitro-β-d-fructopyranose (15), methyl 2,3-O-iso-propylidene-5-O-nitro-α-d-ribofuranoside (16), and 1,2:5,6-di-O-isopropylidene-3-O-nitro-α-d-allofuranose (17) were synthesized by reacting the appropriate triflates (1, 5, 3, 4, and2, respectively) with tetra-butylammonium nitrate in refluxing benzene. These compounds (13-17) and 1,2:4,5-di-O-isopropylidene-3-O-nitro-β-d-fructopyranose (19) also were prepared by reacting the appropriate alcohols (7, 11, 9, 10, 8, and12, respectively) with fuming nitric acid in acetic anhydride. The nitrates13-16and19were photolyzed in 2-propanol to give the corresponding deprotected alcohols. Photolysis of the nitrate17, however, gave the C3inverted alcohol11. A mechanism is proposed for the deprotection and rearrangement of17upon irradiation.

ISSN:0732-8303    

DOI:10.1080/07328308408057899

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

The reaction of 1,2:3,4-di-O-isopropylidene-6-O-triflyl-α-d-galactopyranose (4) with N, N-diphenyl-hydrazine in boiling benzene produced 6-deoxy-1,2:3,4-di-O-isopropylidene-6-(N', N'-diphenylhydrazino)-α-d-galactopyranose (2). The Pyrex-filtered irradiation of2in distilled 2-propanol produced 6-amino-6-deoxy-1,2:3,4-di-O-isopropylidene-α-d-galactopyranose (5) and carbazole. The results obtained show that, while this procedure is a feasible route for aminodeoxy sugar synthesis, product yields are too low for this synthesis to be of general value.

ISSN:0732-8303    

DOI:10.1080/07328308408057900

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

Since the pioneering work of Paulsen et al.1on stereoselective coupling reactions of glucosamine derivatives, the azide function has found general application in carbohydrate chemistry as a nonparticipating masking group for amines. Although excellent results have been reported for the synthesis of α-coupled glucosamine derivatives, the preparation of the required 2-azido-2-deoxy--glucopyranose is often laborious.1c

ISSN:0732-8303    

DOI:10.1080/07328308408057901

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

ISSN:0732-8303    

DOI:10.1080/07328308408057895

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor