Synthetic Approaches to 2,6-trans-Tetrahydropyrans

Abstract

Being different from 2,6-cis-tetrahydropyrans (2,6-cis-THPs), the corresponding 2,6-trans-THPs are thermodynamically less stable and more challenging to construct. The fact that there are many natural products and/or bioactive molecules containing this 2,6-trans-THP subunit has led to the development of many efficient synthetic approaches to access 2,6-trans-THPs. This review summarizes various synthetic methods reported for this structural motif and/or related applications in the total synthesis of natural products.1 Introduction2 Nucleophilic Addition to an Oxocarbenium Ion (Strategy A)3 Intramolecular Oxa-Michael Addition (Strategy B)4 Intermolecular Michael Addition to Dihydropyranones (Strategy A)5 The Heck–Matsuda (Strategy A) Reaction and Oxa-Heck Cyclization (Strategy B)6 Intramolecular SN2 Substitution and Epoxide Opening (Strategy B)7 Miscellaneous Methods8 Conclusion and Outlook

Prins Cyclization: Novel Strategy towards the Diastereoselective Total Synthesis of (–)-Cryptocaryolone

“…We have successfully utilized easily available, metal free, TMSOTf as a catalyst for the Prins cyclisation which is the key step to construct the 2,6-transtetrahydropyran ring and bicyclic lactone in a highly stereoselective manner. 30 General Materials and Methods: Column chromatographic separations were carried out on silica gel (60-120 mesh) and flash chromatographic separations were carried out using 230-400 mesh, silica gel. Mass spectra were recorded on Micromass VG-7070H for EI and VG Autospec M for FABMS.…”

An Overview of Saturated Cyclic Ethers: Biological Profiles and Synthetic Strategies

“…A large number of valuable and high-quality contributions have been made in the construction of THP rings [104,114]. The Prins cyclisation reaction and its variants are extremely powerful methods for constructing THF [115]/THP [116] rings and widely applied in total synthesis [117,118,119].…”

Concise Stereoselective Total Synthesis of (−)-Hedycoropyran A

“…(−)-Hedycoropyran A ( 1 ) is highly oxygenated and, unlike most of diarylheptanoids, possesses a chiral hydroxyl group on the C(7) carbon center adjacent to the trans -2-aryl-6-alkyl-tetrahydro-2 H -pyran framework, which is thermodynamically less stable than the corresponding cis -isomer by virtue of the conformational steric interaction attributable to one carbon substituent being axial and the other equatorial . In fact, a facile epimerization at C(2) of the trans -2-aryl-6-alkyl-tetrahydro-2 H -pyran framework to produce (−)-hedycoropyran B ( 2 ) is prone to occur under acidic conditions, presumably to minimize these unfavorable 1,3-diaxial interactions .…”