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RISS 인기검색어
- 검색키워드
- 저자 : Van-Thoai Pham (검색결과 3 건)
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Studies on the Total Synthesis of (-)-Sedacryptine : (-)-Sedacryptine의 전합성에 관한 연구
Pham, Van Thoai 成均館大學校 大學院 2003 국내박사
Sedacryptine was isolated from Sedum acre, as important alkaloids. This compound is having more complex structure among the other Sedum alkaloids. Although four total synthesis including two diastereoselective asymmetric syntheses have been reported so far, these syntheses have used different synthetic routes for synthesis of sedacryptine, such as by treatment of pyridine cloroformate with acetylide ion which underwent a subsequent Diels-Alder reaction with singlet oxygen; via the double intramolecular conjugate addition of carbamate group; electro-oxidation of the protected hydroxyl Sedamine derivative; Lewis acid-catalyzed ring-opening reaction of semicyclic N,O-acetal possessing an exocyclic nitrogen atom. Recently, we have developed a new Pd(0)-catalyzed synthetic routes for the stereoselective synthesis of an oxazoline from an acyclic allylic and homoallylic amide having a benzoyl substituent as an N-protecting group. The most significant point of this synthesis is the intramolecular reductive amination of a trans-oxazoline by catalytic hydrogenation. By applying the above synthetic methodology herewith we would like to report the stereoselective synthesis of (-)-sedacryptine. Toward the end of total synthesis we got some problems with the reaction. Very soon we will be able to overcome the problem and will report the total synthesis of (-)-sedacryptine.
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Van-Thoai Pham 성균관대학교 대학원 2008 국내박사
1. Total syntheses of (2S, 3R)-3-hydroxypipecolic Acid, D-erythro-sphingosine and (-)-cytoxazone Total syntheses of three vicinal amino alcohol derivatives were describred. (2S,3R)-3-Hydroxypipecolic acid was synthesized by using trans-oxazoline as a chiral building block. Key features involve diastereoselective oxazoline formation catalyzed by palladium(0) and intramolecular cyclization by catalytic hydrogenation of an oxazoline. D-erythro-sphingosine and (-)-cytoxazone were obtained base on high diastereoselective reduction of amino ketone to give the anti- isomer 2. Application of Pd (0)-catalyzed oxazine formation reactions to the total syntheses of natural products Over the past several years, we have been investigating the stereocontrolled synthesis of the trans-oxazoline ring via the highly stereoselective intramolecular cyclization of acyclic allylic and homoallylic amides having a benzoyl substituent as an N-protecting group in the presence of tetrakis(triphenylphosphine) palladium(0) and base (K2CO3). The synthetic utility of these oxazolines as chiral building blocks has been demonstrated by their successful application to the synthesis of β-amino- α-hydroxy and γ-amino-β-hydroxy acids and biologically active natural products such as preussin, sphingofungin F, spectaline, myriocin, L-733060, 1-deoxygalactonojirimycin, 1-deoxygulonojirimycin, threo-sphingosine and (2S, 3R)-3-hydroxypipecolic acid. Recently, we have described a new Pd(0)-catalyzed procedure for the stereoselective formation of an oxazine ring from a -allylic benzamide having a benzoyl substituent as an N-protection group in the presence of Pd(PPh3)4, NaH, and n-Bu4NI. Our study into intramolecular oxazine formation from 1,2-syn-aminoalcohol derivatives has shown that the stereoselectivity of these cyclizations can be critically dependent upon whether the reaction temperature results in kinetic or thermodynamic control of the products. The diastereoselectivity of oxazine ring formation from 1,2-anti-aminoalcohol derivatives is predominantly controlled by the bulkiness R’. I envisioned that these methods could be useful for the preparation of stereodefined hydroxyl amino alcohols and hydroxyl amino acids, and for the preparation of pyrrolidine, piperidine and indolizidine alkaloids: important components of various glycosidase inhibitors. Herein, I wish to report new efficient synthetic routes to -hydroxyisostatine, D-ribo-phytosphingosine, L-lyxo-phytosphingosine, jaspine B, and (-)-lentiginosine.
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