Stereoselective Functionalization of Dihydropyran‐3‐ols: Application to the Synthesis of Enantiopure Ethyl Deoxymonate B

Abstract

The behavior of readily available enantiopure cis and trans 3,6-disubstituted dihydropyran-3-ols and derivatives in epoxidation, osmium-catalyzed dihydroxylations, S N 2Ј, and Claisen-related processes has been examined. The highly diastereoselective dihydroxylation of a suitably function-

Sulfinyl‐Mediated Stereoselective Functionalization of Acyclic Conjugated Dienes

“…Finally, to examine the influencet hat the substitution on the sulfinyl group could have on the stereoselection, 2-methoxynaphthylsulfinyld erivatives 2g and 3g were prepared. Unfortunately, they did not improvethe results mentioned above (Table1,entries [13][14][15][16]. [19] In summary, anti 1,4-diol 11 can be obtained in very high yield and stereoselectivity from dienol 2 using toluene (Table 1, entry 2).…”

“…[14] We presenth erein af ull account of the results of our study on the stereoselective functionalization of acyclic sulfinyl 1,3dienes to produce highly enantioenriched 1,4-diols and 1,4aminoalcohols, via [2,3]-sigmatropic rearrangement of an in situ generated allylic sulfoxide (Scheme1). [15] This transformation renders an et chemo-and stereoselective 1,2-difunctionalization of the terminal double bond in as ulfinyl 1,3-diene, along with removal of the chiral auxiliary.…”

From Allylic Sulfoxides to Allylic Sulfenates: Fifty Years of a Never-Ending [2,3]-Sigmatropic Rearrangement

“… Focusing on 404 , the use of Et 2 NH or Na 2 S led to variable amounts of cis -alcohol 406 and/or ent - 405 , suggesting alternative reaction pathways such as epimerization at C-3 of the starting material or ring-opening/ring-closing sequence, supported by the 66:34 mixture of 406 / ent - 405 found when 397 (R 1 = R 2 = H, R = Ph; Scheme ) was treated with Na 2 S. Finally, 1,4-diazabicyclo[2.2.2]­octane (DABCO) in toluene, a solvent reported to favor the sigmatropic process instead of syn elimination, led to trans -alcohol 405 as a single isomer. The synthetic potential of 3,6-dihydro-2 H -pyran-3-ol derivatives allowed for the application of this methodology to the syntheses of the cores of ent -dysiherbaine, deoxymalayamicin A, and enantiopure ethyl deoxymonate B …”

“…The synthetic potential of 3,6-dihydro-2H-pyran-3-ol derivatives allowed for the application of this methodology to the syntheses of the cores of ent-dysiherbaine, deoxymalayamicin A, 262 and enantiopure ethyl deoxymonate B. 263 The marked difference in behavior of these substrates might be related to the reactive conformations of the diastereomeric allylic sulfoxides. Examination of the J 2,3 coupling constants for 404 and 402 suggests conformer 407 [(H 2 /H 3 ) gauche ] as the preferred arrangement for 404, whereas 408 [(H 2 /H 3 ) anti ] would be preferred for 402.…”

13C NMR Analysis of 3,6-Dihydro-2H-pyrans: Assignment of Remote Stereochemistry Using Axial Shielding Effects

“…This heterocyclic motif is present in a number of natural products, such as aspergillide C ( 6 ), and also serves as a robust synthetic intermediate . The versatility of 3,6-dihydro-2 H -pyrans has enabled the synthesis of a number of important synthetic targets such as the hNK-1 receptor antagonist 7 , ethyl deoxymonate B ( 8 ), and dysiherbaine ( 9 ) . However, the utility of 3,6-dihydro-2 H -pyrans is often impeded by the challenging task of assigning the relative orientation of two substituents located on opposite sides of the ring system.…”