The macrolide (+)-carbonoiide B, the aglycon of the antibiotic carbomycin B, was synthesized via a convergent sequence. A key step of the approach is the union of aldehyde 6 with stannane 7 in the presence of MgBr2.OEt(2) as Lewis acid to afford the C-1-C-9 fragment 26. This chelation-controlled process uses resident stereochemistry at C-4 to control stereochemistry at C-5 and C-6. Elaboration of this fragment at both ends and incorporation of a C-11-C-15 fragment (hydroxy end 4) via esterification and intramolecular Emmons reaction was used to complete the synthesis.
Synthesis of mosesin-4, a naturally occurring steroid saponin with shark repellent activity, and its analog 7-β-galactosyl ethyl cholate
作者:Dario Gargiulo、Timothy A. Blizzard、Koji Nakanishi
DOI:10.1016/s0040-4020(01)89488-6
日期:——
The first synthesis of mosesin-4 (13), a naturally occurring steroid saponin with shark repellent activity, and its analog 19, isdescribed. They both possess a free galactose residue attached axially at the 7α position of the steroidal aglycon. Methyl cholate 3-cathylate (2) was used as a model for exploring various several methods to glycosidate the severely hindered 7α-position. Best results were
Alkylations of chiral amide enolates derived from (ℓ)-prolinol have been shown to yield versatile hydroxy-amides in high diastereomeric purity. Their use in the preparation of optically active carboxylic acids is described.
Total synthesis of the polyether antibiotic ionomycin
作者:David A. Evans、Robert L. Dow、Thomas L. Shih、James M. Takacs、Robert Zahler
DOI:10.1021/ja00169a042
日期:1990.6
A convergent asymmetric synthesis of the calcium ionophore ionomycin has been achieved through a route that is outlined below. The four illustrated subunits, which comprise the c,-C,,-,, CI)-&r cI&22, and C=-C32 portions of ionomycin,
1-Carboxy-(alkanoyl or aralkanoyl)-indoline-2-carboxylic acids, e.g., those of the formula ##STR1## R=H, alkyl, alkoxy, halogeno or CF.sub.3 ; R'=H or R-phenyl; m=0 or 1; p,q=0 to 2; and derivatives thereof, are antihypertensive and cardioactive agents.
First Stereoselective Total Synthesis and Biological Evaluation of Amphidinin B and Its Analogues
作者:Jhillu S. Yadav、A. Srinivas Reddy、Ch. Suresh Reddy、Basi V. Subba Reddy、Venkateshwarlu Saddanapu、Anthony Addlagatta
DOI:10.1002/ejoc.201001205
日期:2011.2
A highly stereoselectivefirsttotalsynthesis of amphidinin B is described. The key steps involved in this synthesis are the generation of the exo-double bond in the C 1 ―C 9 segment, the Barbier allylation, enzymatic kinetic resolution, and the construction of the C 10 ―C 21 segment by Sharpless asymmetric epoxidation, base-induced epoxide ring-opening, radical cyclization, diastereoselective reduction
描述了 amphidinin B 的高度立体选择性的首次全合成。该合成涉及的关键步骤是在 C 1 -C 9 链段中生成外双键、Barbier 烯丙基化、酶动力学拆分以及通过 Sharpless 不对称环氧化反应构建 C 10 -C 21 链段,碱基诱导环氧化物开环、自由基环化、环外双键的非对映选择性还原、一锅烯丙基化随后脱苄基化、Evans 烷基化和 Yamaguchi 酯化。