1. A convenient route to N-[2-(Fmoc)aminoethyl]glycine esters and PNA oligomerization using a Bis-N-Boc nucleobase protecting group strategy
Filip Wojciechowski, Robert H E Hudson J Org Chem. 2008 May 16;73(10):3807-16. doi: 10.1021/jo800195j. Epub 2008 Apr 16.
A simple and practical synthesis of the benzyl, allyl, and 4-nitrobenzyl esters of N-[2-(Fmoc)aminoethyl]glycine is described starting from the known N-(2-aminoethyl)glycine. These esters are stored as stable hydrochloride salts and were used in the synthesis of peptide nucleic acid monomers possessing bis-N-Boc-protected nucleobase moieties on the exocyclic amino groups of ethyl cytosin-1-ylacetate, ethyl adenin-9-ylacetate and ethyl (O(6)-benzylguanin-9-yl)acetate. Upon ester hydrolysis, the corresponding nucleobase acetic acids were coupled to N-[2-(Fmoc)aminoethyl]glycine benzyl ester or to N-[2-(Fmoc)aminoethyl]glycine allyl ester in order to retain the O(6) benzyl ether protecting group of guanine. The Fmoc/bis-N-Boc-protected monomers were successfully used in the Fmoc-mediated solid-phase peptide synthesis of mixed sequence 10-mer PNA oligomers and are shown to be a viable alternative to the currently most widely used Fmoc/Bhoc-protected peptide nucleic acid monomers.
2. Synthesis of Fmoc-Protected ( S, S)- trans-Cyclopentane Diamine Monomers Enables the Preparation and Study of Conformationally Restricted Peptide Nucleic Acids
Hongchao Zheng, Mrinmoy Saha, Daniel H Appella Org Lett. 2018 Dec 7;20(23):7637-7640. doi: 10.1021/acs.orglett.8b03374. Epub 2018 Nov 21.
An efficient synthesis of Fmoc-protected ( S, S)- trans-cyclopentane PNA ( tcypPNA) monomers starting from mono-Boc-protected ( S, S)-1,2-cyclopentanediamine is reported. A general synthetic strategy was developed so that tcypPNA monomers with each nucleobase can be made in sufficient quantity and purity for use in solid-phase peptide synthesis (SPPS). The newly synthesized monomers were then successfully incorporated into 10-residue PNA oligomers using standard Fmoc chemistry for SPPS. The different tcypPNAs allow different positions in the sequence to be conformationally constrained with ( S, S)- trans-cyclopentane to determine the effects on binding to complementary DNA.
3. PNA monomers fully compatible with standard Fmoc-based solid-phase synthesis of pseudocomplementary PNA
Toru Sugiyama, Genki Hasegawa, Chie Niikura, Keiko Kuwata, Yasutada Imamura, Yosuke Demizu, Masaaki Kurihara, Atsushi Kittaka Bioorg Med Chem Lett. 2017 Aug 1;27(15):3337-3341. doi: 10.1016/j.bmcl.2017.06.015. Epub 2017 Jun 3.
Here we report the synthesis of new PNA monomers for pseudocomplementary PNA (pcPNA) that are fully compatible with standard Fmoc chemistry. The thiocarbonyl group of the 2-thiouracil (sU) monomer was protected with the 4-methoxy-2-methybenzyl group (MMPM), while the exocyclic amino groups of diaminopurine (D) were protected with Boc groups. The newly synthesized monomers were incorporated into a 10-mer PNA oligomer using standard Fmoc chemistry for solid-phase synthesis. Oligomerization proceeded smoothly and the HPLC and MALDI-TOF MS analyses indicated that there was no remaining MMPM on the sU nucleobase. The new PNA monomers reported here would facilitate a wide range of applications, such as antigene PNAs and DNA nanotechnologies.
