- A HIGHLY STEREOSELECTIVE CONVERSION OF α,β-EPOXY ESTERS TO α-HYDROXY ESTERS. AN EFFICIENT ROUTE TO OPTICALLY ACTIVE α-HYDROXYESTERS
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α,β-Epoxy esters were cleanly converted to α-hydroxy esters with retention of the configurations at the α-carbon atoms via MgI2-promoted regioselective oxirane ring-opening followed by tributyltin hydride-reduction.
- Otsubo, Kenji,Inanaga, Junji,Yamaguchi, Masaru
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p. 4435 - 4436
(2007/10/02)
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- TRIFLUOROMETHYL GROUP INDUCED HIGHLY STEREOSELECTIVE SYNTHESIS OF α-HYDROXY CARBONYL COMPOUNDS
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The reaction of enolate prepared from ethyl 3-methyl-4,4,4-trifluorobutyrate with MoO5-Py-HMPA complex provides ethyl (2S*,3S*)-2-hydroxy-3-methyl-4,4,4-trifluorobutyrate predominantly.In contrast, NaBH4 reduction of the corresponding 2-oxobutyrate affords (2R*,3S*)-hydroxyester preferentially.
- Morizawa, Yoshitomi,Yasuda, Arata,Uchida, Keiichi
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p. 1833 - 1836
(2007/10/02)
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- Synthesis of piperazine-2,5-diones related to bicyclomycin: 1,4-dibenzyl-3-hydroxy-3-piperazine-2,5-dione. 2. Route via cyclic intermediates
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1,4-Dibenzyl-3-hydroxy-3-piperazine-2,5-dione (43),which incorporates several of the structural features of the antibiotic bicyclomycin, has been synthesized via a reaction sequence involving early construction of the piperazine-2,5-dione ring.In model studies 3-isopropylidenepiperazine-2,5-dione was di-N-benzylated and epoxidized to give 4,7-dibenzyl-2,2-dimethyl-1-oxa-4,7-diazaspirooctane-5,8-dione (10).The opening of the epoxide ring of 10 by several reagents was investigated and it was found that treatment with magnesium isopropylcyclohexylamide (MICA) gives 1,4-dibenzyl-3-hydroxy-3-(1-methylethenyl)piperazine-2,5-dione (23).Treatment of ethyl 3-(2-methoxyethyl)-3-methyl-glycidate (28) with p-toluenesulfonic acid followed by hydrogenation and oxidation gives ethyl 5-methoxy-3-methyl-2-oxopentanoate, which on reaction with chloroacetamide and sulfuric acid followed by treatment of the resulting enamide with ammonia gives (Z)- and (E)-3-(4-methoxybut-2-ylidene)piperazine-2,5-dione.Di-N-benzylation of these followed by epoxidation gives (Z)- and (E)-4,7-dibenzyl-2-(2-methoxyethyl)-2-methyl-1-oxa-4,7-diazaspirooctane-5,8-dione (41 and 42).Treatment of 41 with MICA converts it to compound 43.Chromatography of 43 on silica converts it in part to N-benzyl-N-(2-benzylamino-2-oxoethyl)-3-(2-methoxyethyl)-2-oxo-3-butenamide, which on treatment with MICA regenerates 43.
- Yates, Peter,Hoare, John Harold
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p. 1397 - 1404
(2007/10/02)
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- Ester-Enolate Claisen Rearrangement of Lactic Acid Derivatives
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The ester-enolate Claisen rearrangement of a number of allylic esters of α-hydroxy acids and O-protected derivatives was studied.Crotyl lactate (1b), for example, is converted to the enediolate, silylated, and rearranged to afford the RS,SR and RR,SS dias
- Bartlett, Paul A.,Tanzella, Donna J.,Barstow, James F.
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p. 3941 - 3945
(2007/10/02)
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- Approaches to the Synthesis of Bicyclomycin
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3-Acetoxy-1,4-dibenzyl-3-(3-methoxy-1-methylenepropyl)piperazine-2,5-dione (4) has been synthesized both via cyclization of N-benzyl-N-(N-benzylcarbamoylmethyl)-5-methoxy-3-methylene-2-oxopentanamide (10) and via cleavage of the epoxide ring of 4,7-dibenz
- Hoare, John H.,Yates, Peter
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p. 1126 - 1128
(2007/10/02)
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