Synthesis of Microcolin B, a Potent New Immunosuppressant Using an Efficient Mixed Imide Formation Reaction
摘要:
Microcolin B, a potent new immunosuppressant isolated from blue-green alga Lyngbya majuscula off the Venezuelan coast, has been made using a methyl-directed asymmetric hydrogenation reaction with rhodium on alumina catalyst on lactone 4 for the synthesis of the key (R,R)-2,4-dimethyloctanoic acid fragment 1. A new, direct mixed imide formation reaction was also developed for the production of the unusual prolylpyrrolen-2-one 2 portion of microcolin. The pentafluorophenyl ester of CBZ-proline 5 was reacted with the lithium imidate of lactam 6, providing the mixed imide in 80% yield. Coupling of acid 1 with the N-terminus of the tripeptide, followed by coupling with pyrrolylproline 2, gave microcolin B. The new mixed-imide forming reaction was also applied to a formal total synthesis of microcolin A. The pentafluorophenyl ester of TBS-protected cis-hydroxyproline was coupled with lactam 6, and the resultant imide was converted to the key pyrrolylproline made previously far microcolin A.
Synthesis of Microcolin B, a Potent New Immunosuppressant Using an Efficient Mixed Imide Formation Reaction
摘要:
Microcolin B, a potent new immunosuppressant isolated from blue-green alga Lyngbya majuscula off the Venezuelan coast, has been made using a methyl-directed asymmetric hydrogenation reaction with rhodium on alumina catalyst on lactone 4 for the synthesis of the key (R,R)-2,4-dimethyloctanoic acid fragment 1. A new, direct mixed imide formation reaction was also developed for the production of the unusual prolylpyrrolen-2-one 2 portion of microcolin. The pentafluorophenyl ester of CBZ-proline 5 was reacted with the lithium imidate of lactam 6, providing the mixed imide in 80% yield. Coupling of acid 1 with the N-terminus of the tripeptide, followed by coupling with pyrrolylproline 2, gave microcolin B. The new mixed-imide forming reaction was also applied to a formal total synthesis of microcolin A. The pentafluorophenyl ester of TBS-protected cis-hydroxyproline was coupled with lactam 6, and the resultant imide was converted to the key pyrrolylproline made previously far microcolin A.
Synthesis of <scp>Anti‐Pancreatic</scp> Cancer Natural Product Majusculamide D and Analogues Reveals a Preliminary <scp>Structure‐Activity</scp> Relationships
The total synthesis of majusculamide D (1) was achieved from commercially available materials. In addition, we synthesized eight analogues including three stereoisomers of majusculamide D that differ in the fatty acid chain. Six analogues including a simplified analogue 29 exhibited significant nanomolar-level IC50 values against Panc-1 cells in MTT assays. A preliminary SAR analysis indicated that
majusculamide D ( 1 )的全合成是由市售材料实现的。此外,我们还合成了八种类似物,包括三种脂肪酸链不同的 majusculamide D 立体异构体。在 MTT 测定中,包括简化类似物29在内的六种类似物对 Panc-1 细胞表现出显着的纳摩尔水平 IC 50值。初步的SAR分析表明majusculamide D的C 10 和C 2− C 3 不饱和双键上的羟基对于维持对Panc-1细胞的高活性以及C 40-Me 和C 42-Me基团的定向至关重要是可以忍受的。
Developing microcolin A analogs as biological probes
作者:Amit K. Mandal、John Hines、Kouji Kuramochi、Craig M. Crews
DOI:10.1016/j.bmcl.2005.06.020
日期:2005.9
Three microcolin A and B analogs have been synthesized. Their biological activity profiles were evaluated against several cell lines, revealing the existence of a structural determinant whose role in mediating the antiproliferative effect of the microcolins has heretofore gone unrecognized. While previously described as potent immunosuppressive natural products, we found that these microcolin analogs possessed no selective cytotoxicity when comparing immune cell versus nonimmune cell proliferation. In addition, the amino-terminus of microcolin A has been modified to incorporate a biotinylated polyethylene glycol linker. The biological activity of this biotinylated microcolin A analog was determined. This affinity reagent was shown to retain limited biological activity and thus can serve as a useful probe for elucidating the mechanism of action of microcolin A. (c) 2005 Elsevier Ltd. All rights reserved.