of terminal epoxides followed by their regioselective opening to fix the stereocenters at the C11 and C13 positions, resp., a Pd-catalyzed oxa-Michael reaction to construct the tetrahydropyran ring, and Yamaguchi macrolactonization to form the macrocyclic core of the mol. endobj 13 0 obj [1,4]-S- to O-silyl migration has been used to form silyl enol ethers with Z-configurational control. ͐,.�. Total synthesis of (−)-exiguolide via an organosilane-based strategy. endstream Subsequent work has revealed that acid-sensitive groups such as tetrahydropyranyl (THP)-ethers are deprotected at temperatures higher than −78 °C using this protocol. x�S�*�*T0T0 B�����ih�����]�"� � g to the family of glycosidic macrolides from cyanobacteria. The efficiency of this synthetic strategy was further demonstrated by the concise total synthesis of (±)-diospongin A in 8 steps with 20.2% yield. B. Smith III, B. S. Freeze, I. Brouard, T. Hirose, Org. endstream endstream of the natural product as well as to probe the importance of certain structural features of FR901464 with regard to biol. The reaction mixture was stirred for 1 h at 0 °C and then transferred via cannula to a solution of silyl ketene acetal, L-Selectride (1.0 M in THF, 0.53 mL) was added dropwise to a solution of ketone. Application to glycoside hydrolysis, https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK38XlvFOlug%253D%253D&md5=a24112667f0849fa588930d4e91fe0f6. and represents an increasingly important direction of synthesis focused on achieving function through synthesis-informed design (function-oriented synthesis). on a preparative scale, was crucial to the efficiency of the initial condensation/union reaction, while our efforts toward (-)-kendomycin led to the improved implementation of a modified Kurihara condensation of the β-hydroxy acid and aldehyde involving i-PrOTMS and TMSOTf. 41 0 obj To det. ͐,.�. Diphenyldimethylcyclopentenone and diphenyldimethylcyclopentanone, when dissolved together in equal quantities, formed mixed crystals, perfectly homoegeneous in appearance, melting at 102°-103°, and having a specific gravity which was almost exactly the mean of those of the two pure substances. Highly selective 1,3-asymmetric induction via boron chelates, https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaL2cXmtFWmtb4%253D&md5=ce19a86ebd63074fb58ae8189996c4fe, Experimental design in chemistry: A tutorial, https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD1MXhtF2htbrI&md5=96fa3682fbc783567ea54b72af2c8fce, An Efficient Synthesis of 4-(Phenylsulfonyl)-4H-furo[3,4-b]indoles, https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD38XjsFektA%253D%253D&md5=6ddf3971bed0a73f8114f131075532d3, Molecular mechanical investigations of the properties of oxocarbenium ions. endstream 16 0 obj <>stream Hongze Li, Hengmu Xie, Zhigao Zhang, Yongjin Xu, Ji Lu, Lu Gao, Zhenlei Song. endstream 29 0 obj II. endobj The authors reviewed in part their computational, design, synthesis, and biol. Dalgard, Jackline E.; Rychnovsky, Scott D. A cationic cascade reaction has been developed that produced 4-tetrahydropyranones, e.g., I, in good yield. By what mechanism do acids deprotect primary silyl ethers? of α,β-unsatd. x�s �r� x�s Scope of the Tetrahydropyran-4-one Synthesis with Different Aldehydes and Alcohols, with Varying Substituents at the C-3 Position, The stereoselective outcome of the THPO cyclization reaction was further examined with substitution at C-5. Addn. ��w3T�PI�2T0 BCcC#=s#c��\. 23 0 obj A general and highly enantioselective synthesis of trans-2,5-diarylfurans, potent antagonists of platelet activating factor, also illustrates the value of this enantioselective redn. �r� The synthesis of (-)-I was achieved in 15 linear steps (12% overall yield), exploiting a modification of the Petasis-Ferrier rearrangement to construct the C(11-15) cis-tetrahydropyran. This reaction provides a concise and selective means to form tetrahydropyran-contg. ͐,.�. Prins cyclization during the TMSOTf-promoted union process, unless suitably protected. Does learning the same spell from different sources allow it to benefit from bonuses from all sources? <>stream B.; Thomas, M.; Wirtz, C.; Dubost, C.; Handa, S.; Fürstner, A. endobj The silyl enol ether Prins reaction is highly diastereoselective with most substrates, and the major products are consistent with cyclizations through chairlike transition states.