Syntheses of (−)-Funebrine and (−)-Funebral, Using Sequential Transesterification and Intramolecular Cycloaddition of a Chiral Nitrone
作者:Osamu Tamura、Nobutaka Iyama、Hiroyuki Ishibashi
DOI:10.1021/jo030257q
日期:2004.3.1
The first syntheses of (−)-funebrine [(−)-1] and (−)-funebral [(−)-2] are described. The syntheses feature sequential formation of nitrone VI frommethyl glyoxylate (5) with oxime 6, transesterification of nitrone VI with (E)-crotyl alcohol (4), and intramolecular cycloaddition of the resulting nitrone VII bearing crotyl ester to afford cycloadduct 7 as a major product. The adduct 7 was readily elaborated
Synthesis of Enantiomerically Pure Isoxazolidine Monomers for the Preparation of<i>β</i><sup>3</sup>-Oligopeptides by Iterative<i>α</i>-Keto AcidHydroxylamine (KAHA) Ligations
作者:Ying-Ling Chiang、Justin A. Russak、Nancy Carrillo、Jeffrey W. Bode
DOI:10.1002/hlca.201200484
日期:2012.12
for the synthesis of enantiomerically pure isoxazolidine monomers for the synthesis of β3‐oligopeptides via α‐keto acidhydroxylamine (KAHA) ligation is presented. This one‐pot synthetic method utilizes in situ generated nitrones bearing gulose‐derived chiral auxiliaries for the asymmetric 1,3‐dipolar cycloaddition with methyl 2‐methoxyacrylate. The resulting enantiomerically pure isoxazolidine monomers
Stereoselective vinylogous Mannich reaction of 2-trimethylsilyloxyfuran with L-gulose-derived chiral nitrones in the presence of a catalytic amount of trimethylsilyl trifluoromethanesulfonate was investigated. The selectivity was strongly influenced by the bulkiness of the C-substituent of the nitrone: for example, C-benzyloxymethyl nitrone afforded four stereoisomers, whereas bulky C-[(4S)-2,2-dimethyl-1,3-dioxolan-4-yl]nitrone gave a single stereoisomer. The latter product was elaborated to afford key synthetic intermediates for polyoxin C and dysiherbaine.
研究人员在催化剂量的三氟甲磺酸三甲基硅酯存在下,研究了 2-三甲基硅氧基呋喃与 L-古洛糖衍生的手性腈的立体选择性乙烯基曼尼希反应。腈酮的 C-取代基的体积对选择性有很大影响:例如,C-苄氧基甲基腈酮可生成四种立体异构体,而体积较大的 C-[(4S)-2,2-二甲基-1,3-二氧戊环-4-基]腈酮只能生成一种立体异构体。对后一种产品进行了详细加工,以获得聚氧乙烯醚 C 和地西海因的关键合成中间体。
Nucleophilic Addition Reaction of 2-Trimethylsilyloxyfuran to <i>N</i>-Gulosyl-<i>C</i>-alkoxymethylnitrones: Synthetic Approach to Polyoxin C
[GRAPHICS]The stereoselectivity of nucleophilic addition of 2-trimethylsilyloxyfuran to N-gulosyl-C-alkoxymethylnitrones was investigated. It was found that the selectivity was highly dependent on the bulkiness of the C-substituent of the nitrone. The major adducts were elaborated into the key intermediate of polyoxin C.