- Synthetic Marine Sponge Collagen by Late-Stage Dihydroxylation
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Based on the observation that an increased substrate size is paralleled by an enhanced diastereoselectivity, a late-stage dihydroxylation protocol toward the 21mer CMP (collagen model peptide) Ac-(Pro-Hyp-Gly)3-Pro-Dyp-Gly-(Pro-Hyp-Gly)3-NH2 is presented. C3 and C4 hydroxylation have a converse effect on the triple-helical stability of collagen. Their combined influence on the melting temperature was studied by NMR spectroscopy.
- Priem, Christoph,Geyer, Armin
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p. 162 - 165
(2018/01/17)
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- Nucleophilic fluorination of triflates by tetrabutylammonium bifluoride
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(Chemical Equation Presented) Careful examination of nucleophilicity, basicity, and leaving group ability led us to discover the nucleophilic fluorination of triflates by weakly basic tetrabutylammonium bifluoride, which provides excellent yields with minimal formation of elimination-derived side products. Primary hydroxyl groups as well as secondary hydroxyl groups in acyclic chains or in five-membered rings are excellent substrates, whereas benzylic and aldol-type secondary hydroxyl groups give poor yields as a result of the instability of their triflates.
- Kim, Kyu-Young,Bong, Chan Kim,Hee, Bong Lee,Shin, Hyunik
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p. 8106 - 8108
(2008/12/22)
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- METHOD FOR PRODUCING FLUORINATED PROLINE DERIVATIVE
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Disclosed is a method for efficiently producing a high-purity fluorinated proline derivative with high yield. Specifically disclosed is a method for producing a compound represented by the general formula (2) below wherein a compound represented by the formula (1) below is reacted with a fluorination agent, and then chlorine, bromine, iodine, hypochlorous acid, hypochlorite, hypobromous acid, hypobromite or N-halogenosuccinimide is caused to act on the reaction product obtained by the preceding reaction and containing the compound represented by the general formula (2) below and a by-product for chemically changing the by-product. (1) (In the formula (1), R1 represents an unsubstituted or substituted alkyl group having 1-6 carbon atoms or the like; R2 represents an unsubstituted or substituted alkyl group having 1-6 carbon atoms or the like; and R3 represents a hydroxyl group or the like.) (2) (In the formula (2), R1 and R2 are as defined above.)
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Page/Page column 36-38
(2008/06/13)
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- Synthetic studies toward astins A, B and C. Efficient syntheses of cis- 3,4-dihydroxyprolines and (-)-(3S,4R)-dichloroproline esters
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Efficient syntheses of the esters of cis-3,4-dihydroxyprolines and the first synthesis of the ester of the rare amino acid (-)-(3S,4R)- dichloroproline from trans-4-hydroxy-L-proline are presented. The synthetic route provides easy access to several substituted prolines and cis- hydroxylated proline esters. Various types of biological activities have been associated with these substituted prolines. The role of (-)-(3S,4R)- dichloroproline in astins A, B and C is under investigation.
- Schumacher, Kelly K.,Jiang, Jianjun,Joullie, Madeleine M.
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