摘要:

AbstractThe synthesis is described of a series of twenty 17‐(isocyanotosylmethylene) steroids5from 17‐oxo steroids and 4‐tolylsulfonylmethyl isocyanide (TosMIC). Furthermore, nine analogous 17‐(isocyanosulfonylmethylene) steroids (15–21a) have been prepared using sulfonylmethyl isocyanides other than TosMIC. The synthesis of four new TosMIC analogues is

ISSN:0165-0513    

DOI:10.1002/recl.19911101002

出版商:WILEY‐VCH Verlag    

年代:1991

数据来源: WILEY

摘要:

Abstract3,3‐Dimethyl‐2‐butanone (pinacolone) was converted in a two‐pot, three‐step process in 67% overall yield into (E)‐1‐isocyano‐2,3,3‐trimethyl‐1‐tosyl‐1‐butene (1), or 1‐isocyano‐3,3‐dimethyl‐2‐methylene‐l‐tosylbutan(2), as an important departure from the previously reported one‐pot conversion to 2,3,3‐trimethylbutanenitrile (13). In addition, the

ISSN:0165-0513    

DOI:10.1002/recl.19911101003

出版商:WILEY‐VCH Verlag    

年代:1991

数据来源: WILEY

摘要:

AbstractDeprotonation of 6‐demethoxythebaine (1) with butyllithium, followed by reaction of the anion with dimethyl sulfate, gave the non‐conjugated diene4as the major product and title compound 5β‐methyl‐6‐demethoxythebaine (5) only in low yield. Therefore,5was prepared from 5β‐methylthebaine (6), which was converted into 5β‐methylcodeinone (7) and then reduced to 5β‐methylcodeine (8). Mesylation of8yielded 6‐O‐mesyl‐5β‐methylcodeine (9). Reaction of9with lithium bromide gave 5β‐methyl‐bromocodide (10) as the major product, together with5. When10was treated with potassiumtert‐butoxide, the desired5was obtained in good yield. Short treatment of10gave the intermediate 8‐bromo‐5‐methyl‐desoxycodeine‐A (11), which reacted further to5after prolonged treatment.Diels‐Alder reaction of 5 with ethyl acrylate yielded two products, ethyl 6α,14α‐ethenoisomorphinan‐7α‐carboxylate 13 and ethyl 6β,14β‐ethenomorphinan‐8β‐carboxylate 14, due to β‐face and α‐face approach, respectively. Similarly, with 3‐buten‐2‐one as the dienophile, a mixture of 7α‐acetyl‐6α,l4α‐ethenoisomorphinan 15 and 8β‐acetyl‐6β,14β‐ethenomorphinan 16 was obtained. Diels‐Alder reaction of 5 with maleic anhydride, followed by esterification of the adducts, yielded dimethyl 6α,l4α‐ethenoisomorphinan‐7β,8β‐dicarboxylate 19 and dimethyl 60,140‐ethenomorphinan‐7β,8β‐dicarboxylate 20 in a 7 : 3 ratio.

ISSN:0165-0513    

DOI:10.1002/recl.19911101004

出版商:WILEY‐VCH Verlag    

年代:1991

数据来源: WILEY

摘要:

AbstractD‐(+)‐xylose has been converted to (+)‐sesbanimide A in sixteen steps. The synthetic scheme involves an unusual tricyclic silylated derivative (9a) of the monobenzoylated product of the earlier described glutarimide intermediate (7). Compound9ais a pivotal intermediate for the construction of ring C of (+)‐sesban

ISSN:0165-0513    

DOI:10.1002/recl.19911101005

出版商:WILEY‐VCH Verlag    

年代:1991

数据来源: WILEY

摘要:

AbstractThe reductive cleavage reaction of functionalised triphenylphosphines1–34with Na/NH3and Li/THF depends strongly on the nature of the functionality and on the reducing agent. No reduction occurs with11, 24, 30, 31 and 32in Na/NH3. Compounds3, 4, 5, 10, 12, 13, 15, 19, 23, 25, 26and27cleave to give the secondary phosphide in high yield with Na/NH3, whereas2, 7and9give a high yield with Li/THF. Reduction occurs but cleavage is poor with6, 7, 14, 29and34and Na/NH3, or with11and Li/THF. Primaryortho‐functionalised phenyl phosphines are obtained by a double cleavage reduction from2, 5, 12, 25, 26and27with Na/NH3. This unprecedented reaction proceeds via the secondary phosphine, which is formed by protonation of the corresponding phosphide with NH3. It occurs when the aryl group contains a strongly electron‐donating substituent. Multiple cleavage of aryl groups with extended π systems occurs with7and34when they are made to react with Li/THF. Halogens are cleaved from the phenyl group (16, 17, 18, 28 and 33, with Na/NH,), whereas SCH, groups are converted to the corresponding mercapto group (20, 21 and 22). Birch reduction (2 and 10) can take place in NH, but not in the aprotic solvent THF; it occurs only when other reactions are slow. Sodium amide is obtained via reaction of 8 in Na/NH,. Restricted Hartree‐Fock calculations were carried out for a number of substituted phenylphosphines. From the correlation between the energies and coefficients of the LUMO (always an aryl π* orbital) and the experimental cleavage data, it was concluded that there are three requirements for successful cleavage. The LUMO energy should be neither too high (no reduction) nor too low (radical anion too stable) and, further, the coefficient of the LUMO on the carbon attached to phosphorus must

ISSN:0165-0513    

DOI:10.1002/recl.19911101006

出版商:WILEY‐VCH Verlag    

年代:1991

数据来源: WILEY

摘要:

AbstractThe regioselective acylation of adenosine by phenylalanine was carried out using subtilisin in reverse mode. Under ultrasonic irradiation, the bioconversion affords only the S' aminoester.

ISSN:0165-0513    

DOI:10.1002/recl.19911101007

出版商:WILEY‐VCH Verlag    

年代:1991

数据来源: WILEY

摘要:

Abstract5′‐O‐Methoxyacetyl‐3′‐O‐methylthiomethylene‐2′‐deoxy‐uridine could be condensed with 3′‐O,N3‐di‐benzoyl‐thymidine using NISI cat.TfOH as the activating system, to give the (3′→ 5′) methylene acetal linked dinucleoside. After removal of the methoxyacetyl group and tritylation of the 5′‐hydroxyl function, the uridine moiety was converted into cytidineviathe corresponding 4‐triazolo analogue. SubsequentN4‐benzoylation of cytidine and phosphitylation of the 3′‐terminus afforded

ISSN:0165-0513    

DOI:10.1002/recl.19911101008

出版商:WILEY‐VCH Verlag    

年代:1991

数据来源: WILEY

ISSN:0165-0513    

DOI:10.1002/recl.19911101001

出版商:WILEY‐VCH Verlag    

年代:1991

数据来源: WILEY