Question: Zaragozic acids are a group of structurally
Zaragozic acids are a group of structurally related, natural products that were first isolated from fungal cultures in 1992. These compounds have been shown to reduce cholesterol levels in primates, an observation that has fueled interest in the synthesis of zaragozic acids and their derivatives. During a synthesis of zaragozic acid A, compound 1 was treated with NMO and catalytic OsO4 to afford intermediate 2, which quickly rearranged to give compound 3. The conversion of 1 to 2 was observed to proceed in a diastereoselective fashion. That is, syn addition only occurs on the top face of the Ï€ bond, not on the bottom face. Provide a justification for this facial selectivity. You might find it helpful to build a molecular model. 
Transcribed Image Text:
но HO- OH HO OSEM OH OSEM Os0, (catalytic) NMO но- но OSEM SEM = CH,OCH;CH,Si(CH,)s 3
> Consider the following two compounds. When treated with NaOH, one of these compounds forms an epoxide quite rapidly, while the other forms an epoxide very slowly. Identify which compound reacts more rapidly and explain the difference in rate between the
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> Predict the product of the following reaction: Me 1) LIAID. ? Me 2) H,0
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> Propose a structure for a compound with the molecular formula C4H8O that exhibits the following 13C NMR and FTIR spectra: Carbon NMR 07.7 25.4- 80 70 10 60 Chemical shift (ppm) 100 90 50 40 30 20 100 80 60 40 20 0- 4000 2500 3500 3000 2000 1500 1000
> Propose a structure for a compound with the molecular formula C8H18O that exhibits the following 1H NMR and 13C NMR spectra: Proton NMR 3 2.0 Chemical shift (ppm) 4.0 3.5 3.0 2.5 1.5 1.0 0.5 Carbon NMR -70.5 31.6- 19.3- -13.7 70 60 50 40 30 20 10 Che
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> Propose a structure for an ether with the molecular formula C7H8O that exhibits the following 13C NMR spectrum: Carbon NMR 129.5- 120.7 55.1- 159.7- 160 140 120 100 80 60 40 Chemical shift (ppm)
> Propose an efficient synthesis for each transformation. (a) OH (b) (c) CI (d) CI Xor (e) HO. OH OH (f) (h) + En (k) (0) OH (m) OH (n) LOH (о) HO. (p) 'CI он (9) CI H. он (r) OH HO, (s) + En (t) OH + En (u) OMe
> Consider the following compound: a. How many signals do you expect in the 1H NMR spectrum of this compound? b. Rank the protons in terms of increasing chemical shift. c. How many signals do you expect in the 13C NMR spectrum? d. Rank the carbon atoms
> Using compounds that possess no more than two carbon atoms, propose an efficient synthesis for the following compound:
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> When the following chiral epoxide is treated with aqueous sodium hydroxide, only one product is obtained, and that product is achiral. Draw the product and explain why only one product is formed. NaOH H,0 ? Me 'Me
> Fill in the missing products below 1) Hg(OAc)2, EIOH Excess HỊ ? 2) NABH, Нeat ? RCO,H H-CEC: Na ? ? 1) NaSEt 2) H,0 ? HBr
> Fill in the missing reagents below. OH Me OH ? HO OEt ? |? ? Br OH HO, SMe Me OEt ? ? OMe DEt OH OH CN
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> Show reagents that can be used to achieve the following transformation:
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> Deduce the structure of a compound with the molecular formula C12H8Br2 that exhibits the following 1H NMR and 13C NMR spectra: Proton NMR Expansion 78 76 7.4 7.2 TMS 10 8 6 5 2 Chemical Shift (ppm) Carbon NMR Solvent- Proton decoupled 200 160 120 80
> 68. What are the best reagents to perform this transformation? a. Na2Cr2O7, H2SO4, H2O b. CrO3, H3O+, acetone c. PCC, CH2Cl2 d. KMnO4, NaOH, cold 69. Which of the following is NOT an efficient synthesis of 2-methyl-2-pentanol? 70. What is the produc
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> 68. Which of the following methods can be used to prepare this compound? 69. Which is an intermediate in the mechanism for the following reaction? 70. Which is a product of this reaction? Br ON NaOH (a) Hg(OAc)a. NaBH4 -OH (b) NaH (c) OH -Br NaH (d
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> Deduce the structure of a compound with the molecular formula C5H10O that exhibits the following IR, 1H NMR, and 13C NMR spectra. Data from the mass spectrum are also provided. 100 - Mass Spec. Data relative miz abund. 80 15 23 26 20 27 61 29 92 30
> Deduce the structure of a compound with the molecular formula C8H10O that exhibits the following IR, 1H NMR, and 13C NMR spectra: 100 80 60 40 20 2000 Wavenumber (cm) 4000 3500 3000 2500 1500 1000 Proton NMR 2 2 7 5 2 Chemical Shift (ppm) Carbon NMR
> Using any compounds that have no more than two carbon atoms, identify a method for preparing each of the following compounds: он OH (a) (b) он (c) OH (d)
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> Using any reagents of your choosing, show how you would convert tert-butyl alcohol into 2-methyl-1-propanol.
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