Efficient Asymmetric Synthesis of Biologically Important Tryptophan Analogues via a Palladium-Mediated Heteroannulation Reaction
作者:Chunrong Ma、Xiaoxiang Liu、Xiaoyan Li、Judith Flippen-Anderson、Shu Yu、James M. Cook
DOI:10.1021/jo001679s
日期:2001.6.1
A novel and concise synthesis of optically active tryptophan derivatives was developed via a palladium-catalyzed heteroannulation reaction of substituted o-iodoanilines with an internal alkyne. The required internal alkyne 14a or 25 was prepared in greater than 96% de via alkylation of the Schöllkopf chiral auxiliary 19 employing diphenyl phosphate as the leaving group. The Schöllkopf chiral auxiliary
Enantioselective synthesis of non-proteinogenic amino acids via metallated bis-lactim ethers of 2,5-diketopiperazines
作者:Ulrich Schöllkopf
DOI:10.1016/s0040-4020(01)91926-x
日期:1983.1
excess = asymmetric induction) of the adduct exceeds 95%. On hydrolysis the adducts are cleaved liberating the chiral auxiliary (used to build up the bis-lactim ether 1) and the target molecules, the opticallyactive amino acid methyl esters of type 8,19,25 or 36. The two amino acid esters are separable either by fractional distillation or (eventually after further hydrolysis to amino acids) by chromatography
A general method for the facile synthesis of optically active 2-substituted piperazines via functionalized 2,5-diketopiperazines
作者:Kate S. Ashton、Mitchell Denti、Mark H. Norman、David J. St. Jean
DOI:10.1016/j.tetlet.2014.06.058
日期:2014.8
Upon utilization of some common methods described in the literature for the synthesis of chiral, 2-substituted 2,5-diketopiperazines, extensive racemization was observed. Further investigation showed that heating in the presence of a mild base racemized the chiral center in the product diketopiperazines. A generalized, readily scalable route was sought and, after investigating the effect of base and
Aqueous in situ one-pot N-Boc-deprotection-cyclization of N alpha-Boc-dipeptidyl-tert-butyl and methyl esters under microwave irradiation afforded 2,5-diketopiperazines (DKPs) in excellent yields. This protocol is rapid, safe, environmentally friendly, and highly efficient, and showed that the tert-butoxy moiety is also an excellent leaving group for these cyclizations.
Entry into 6-Methoxy-D(+)-tryptophans. Stereospecific Synthesis of 1-Benzenesulfonyl-6-methoxy-D(+)-tryptophan Ethyl Ester
作者:Michael S. Allen、Linda K. Hamaker、Anthony J. La Loggia、James M. Cook
DOI:10.1080/00397919208021343
日期:1992.7
Abstract A strategy for the synthesis of optically active ring-A methoxylated indole alkaloids which employs the Moody azide/Schollkopf chiral auxiliary protocol has resulted in the successful preparation of 1-benzenesulfonyl-6-methoxy-D(+)-tryptophan ethyl ester 16. This amino ester is required for the synthesis of Alstonia bisindole alkaloids including macralstonine 2 via an enantiospecific Pictet-Spengler