A concise synthesis of the novel antibiotic aranorosin
作者:Alexander McKillop、Lee McLaren、Robert J. Watson、Richard J.K. Taylor、Norman Lewis
DOI:10.1016/s0040-4039(00)73870-6
日期:1993.8
A short synthesis of the novel antibiotic aranorosin is described which employs a novel hypervalent iodine-mediated oxidative hydroxylation of a tyrosinal derivative in the key step. A similar procedure was employed to prepare 6′-epiaranorosin, and hence establish the stereochemistry of the natural compound.
Application of the diastereoselective photodeconjugation of α,β-unsaturated esters to the synthesis of gymnastatin H
作者:Ludovic Raffier、Olivier Piva
DOI:10.3762/bjoc.7.21
日期:——
The asymmetric synthesis of gymnastatin H has been achieved by using the photoisomerisation of a conjugated ester to its beta,gamma-unsaturated isomer through the protonation of a in situ generated dienol as key step. Thanks to diacetone D-glucose used as a chiral alkoxy group, the protonation occurred well onto one of the two diastereotopic faces with very high yields and selectivities. Moreover,
Gynastatin H 的不对称合成是通过使用共轭酯的光异构化为其 β,γ-不饱和异构体通过原位生成的二烯醇的质子化作为关键步骤来实现的。由于双丙酮D-葡萄糖用作手性烷氧基,质子化以非常高的产率和选择性很好地发生在两个非对映体之一上。此外,通过这种方式控制了目标分子的 C-6 中心的构型。
Total synthesis and structure assignment of the antitumor antibiotic aranorosin
作者:Peter Wipf、Yuntae Kim、Paul C. Fritch
DOI:10.1021/jo00077a050
日期:1993.12
The structurally unique antifungal and antitumor antibiotic aranorosin was prepared in a convergent, stereoselective sequence. Oxidative cyclization of N-protected L-tyrosine, followed by face-selective 1,2-addition of [(benzyloxy)methyl]lithium, Henbest oxidation in the presence of Kishi's radical inhibitor, and simultaneous N,O-deprotection led to an amino diol which was N-acylated with the fatty acid side-chain segment. After a low-temperature reduction of the lactone moiety to the lactol, the carbonyl function was regenerated under neutral conditions by diol cleavage with sodium periodate. Preparation of the acid side chain involved a diastereoselective imide alpha-alkylation directed by Evans' oxazolidinone auxiliary, followed by a series of Wittig-Horner chain extensions. Since the relative configuration at the C (6') position of the natural product had not been determined, we prepared both the (6'S) and the (6'R) isomers of aranorosin. Comparison of synthetic material with the reported spectral data for natural (-)-aranorosin, especially H-1 and C-13 NMR and [alpha]D, did not allow a definitive assignment. After purification of a sample of the isolated material from Pseudoarachniotus roseus, the corrected [alpha]D strongly indicated the (6'R)-stereochemistry for the natural compound. This assignment was confirmed by circular dichroism spectra for (6'S)- and (6'R)-aranorosin and the natural material.