Cyclization of Synthetic seco‐Proansamitocins to Ansamitocin Macrolactams by Actinosynnema pretiosum as Biocatalyst

Abstract

Conventional solid films on certain substrates play a crucial role in various applications, for example in flat panel displays, silicon technology, and protective coatings. Recently, tremendous attention has been directed toward the thinning and shaping of solids into so‐called nanomembranes, offering a unique and fantastic platform for research in nanoscience and nanotechnology. In this Review, a conceptual description of nanomembranes is introduced and a series of examples demonstrate their great potential for future applications. The thinning of nanomembranes indeed offers another strategy to fabricate nanomaterials, which can be integrated onto a chip and exhibit valuable properties (e.g. giant persistent photoconductivity and thermoelectric property). Furthermore, the stretching of nanomembranes enables a macroscale route for tuning the physical properties of the membranes at the nanoscale. The process by which nanomembranes release from a substrate presents several approaches to shaping nanomembranes into three‐dimensional architectures, such as rolled‐up tubes, wrinkles, and the resulting channels, which can provide fascinating applications in electronics, mechanics, fluidics, and photonics. Nanomembranes as a new type of nanomaterial promise to be an attractive direction for nanoresearch.

Biomimetic Thioesters as Probes for Enzymatic Assembly Lines: Synthesis, Applications, and Challenges

“…EDC and DCC are sometimes also combined with 1-hydroxybenzotriazole (Chamberland et al, 2009;Prasad et al, 2012;Wang et al, 2015). Instead of DCC, the related reagent diisopropylcarbodiimide (DIC) has also been used successfully (Harmrolfs et al, 2010;Taft et al, 2009). In addition, diphenylphosphoryl azide (DPPA) (He et al, 2006;Iida et al, 2008;Sandy et al, 2013;Yamada et al, 1974), carbonyldiimidazole (CDI) (Deska et al, 2011;Hartung et al, 2005;Klopries et al, 2013), and (benzotriazol-1-yloxy)tripyrrolidinophosphonium hexafluorophosphate (PyBOP) (Haynes et al, 2011;Schneider et al, 2003;Strieter et al, 2009) are commonly used.…”

Broad Substrate Specificity of the Amide Synthase in S. hygroscopicus—New 20-Membered Macrolactones Derived from Geldanamycin

“…The second set of mutaproducts, three 20-membered macrolactones, revealed an unexpected and unprecedented chemoselectivity of the amide synthase responsible for macrocyclization, which is not shown by the corresponding amide synthase operating in ansamitocin biosynthesis. 15,16 This substrate flexibility with respect to the aryl moiety of the bound nucleophile could be extended using other m -hydroxymethylbenzoic acid starter units. Finally, new geldanamycin derivatives 8 , 11 and 12 show good to moderate antiproliferative activities on different cell lines while partially post-PKS processed mutaproducts 9 and 10 have lost most of this biological property.…”

First Ring‐Expanded Maytansin Lactone Accessed by a New Mutasynthetic Variant

“…AHBA 1 is formed from UDP‐glucose through a unique variation of the shikimate acid pathway (Scheme ) . Processing through seven PKS modules furnishes seco ‐proansamitocin that undergoes macrolactamization by an amide synthase that is not part of the PKS to yield proansamitocin ( 2 ) . Finally, six tailoring steps provide ansamitocin P‐3 ( 3 ) .…”

“…[9] Processing through seven PKS modules furnishes seco-proansamitocin that undergoes macrolactamization by an amide synthase that is not part of the PKS to yield proansamitocin (2). [10,11] Finally, six tailoring steps provide ansamitocin P-3 (3). [10] Commonly, the protocols can be conducted with unmodified benzoic acids, because activation to the corresponding SCoA esters occurs before the in vivo uploading onto the PKS.…”

“…These results suggest that this amide synthase may become a chemical tool of interest for performing macrocylizations. [11]…”