โ Scribed by L.H. Zalkow; E. Keinan; S. Steindel; A.R. Kalyanaraman; J.A. Bertrand
No coin nor oath required. For personal study only.
Toxol, (-)-2-iso-propenyl-3-hydroxy-5-acetyl-2,3-dihydrobenaofuran, isolated from
Aplopappus heterophyllus, has been reported to have the 2S, 3s configuration (T,3d-OH)2'3. -3 OR +=s 0 0 2 l-While the configurational assignment at C-2 has been correlated with several compounds of known absolute configuration', the assignment at C-3 was based on one experimental observation, namely, II trans:-OR'(P) III cis:--OR'(6) the ozonolysis of toxol to yield supposedly (+) tartaric acid 2.3 . The present work shows that the configuration of toxol at C-3 must be reassigned as i (I, 38-OH).
We recently reported the synthesis of racemic erans (II:R-COCH3,R1=H) and c&-2-isopropyl-3hydroxy-5-acetyl-2,3-dihydrobenaofurans (III:R-CCCH3,R1-H)4. The isomer, which was spectrally identical with dihydrotoxol was assigned a cis relationship at C-2.63. This assignment lad to an unexpected consequence, namely, in synthetic dihydrotoxol and all of its precursors (III:R=Br, Rl=H; R=Br,R1=COCH3; R=C02H,R1-H; R=COCH3,R1-COCH3) the coupling constant for the vicinal C-2, c-3 protons was consistently smaller (513-4.5 vz 5-6 Hz) than in the isomeric trans series (II:R=Br,Rl-II; R=Br,Rl-COCR 3; R=COCH~,R~=H), in apparent violation of the Karplus equation5.
Since it had been observed that J cis? Jtrans for 2-alkyl-3-methyl-2,3-dihydrobenaofurans6, the
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The complete analysis of the 'H NMR spectra of [ (C,Me,)lr(glycinate)CI] and [ (C,Me,)Ir(N-methyl-g1ycinate)Clj provide information for the conformational analysis of the five-membered N-C-C-0-Ir ring. A Karplus relationship has been established for these metallacycles [ 3J(H,H) = 8.9 cos' 4 -1.0 c
## Abstract The ^1^H and ^13^C NMR spectra of some alkyl carboxylates of aminoโsubstituted dihydrobenzoxazepine thiones and dihydrobenzodiazepine thiones were recorded in CDCI~3~, and DMSO solutions, and the complete spectral assignments performed with 1D and 2D techniques. A solventโdependent taut