2- Hydroxy-1 -isopropenyl

Benzo[6]furan, 5-acetyl-6-hydroxy-2-isopropenyl-UV, 4, 589 (71AJ093)... 

Hydroxy-3-methoxy-tctramethyl- 669 di-2-Hydroxymethyl-1 -methoxyearbonyl- 153 2-lsocyanat-2-methyl-1,1-diphenyl - 123 Isopropenyl- 67. 69... 

Hydroxy-butyl)-l-( -hydroxy-benzyl)- 296 Hydroxylamino- 474, 682 4-Hydroxylamino-l-athylthio- 684 Hydroxylamino-alk(aryl)oxy- 684 2-Hydroxylamino-1 -isopropenyl- 698 4-Hydroxyl amino-1 -methyl- 683 4-Hydroxylamino-1 -methylthio- 684 2-Hydroxylamino-l-nitro- 562 2-Hydroxylamino-l-[penten-(l)-yl-(2)J- 698 4-Hydroxylamino-l-phenylthio- 684 4-Hydroxylamino-1 -sulfonyl- 683 Hydroxymethyl- 499... 

In a pyrogram of Bisphenol A poly(formal) (6), the peak products are identified as a-methylstyrene, phenol, 4-hydroxy-a-methylstyrene, and isopropyl phenol by Py-GC/MS. These products are identical with the degradation products from Bisphenol A. In addition to the decomposition products of Bisphenol A, 4-isopropenyl anisole is also identified as a product. The pyrograms of Bisphenol AF poly(formal) (7) contain only two major species, pentafluoroisopropenyl benzene (product T) and pentafluoroisopropenyl anisole (product 2 ). They correspond to a-methylstyrene, 4-hydroxy-amethylstyrene from Bisphenol A poly(formal) (6) and are produced by the cleavage of phenylene-oxy bonds and oxy-methylene bonds according to (Scheme 6). 

The alternative method for making activated esters is base-catalyzed transesterification. Fmoc-amino acids are esterified in excellent yields by reaction with pentafluorophenyl trifluoroacetate at 40°C in the presence of pyridine (Figure 7.13). A mixed anhydride is formed initially, and the anhydride is then attacked by the pentafluorophenoxy anion that is generated by the pyridine. Succinimido, chlorophe-nyl, and nitrophenyl esters were made by this method when it was introduced decades ago. A unique variant of this approach is the use of mixed carbonates that contain an isopropenyl group [Cf C CfyO-COjR]. These react with hydroxy compounds in the presence of triethylamine or 4-dimethylaminopyridine (see Section 4.19) to give the esters and acetone.30 35... 

Other furocoumarins, although they have rather different structures, have very similar names, which gives rise to confusion. Thus, whereas oroselone (8) is 8-isopropenyl-2//-furo[2,3-A][l]benzopyran-2-one12 and oroselol (9) is 8-(l-hydroxy-l-methylethyl)-2 -furo[2,3- ][l]benzopy-ran-2-one, oreoselone (10) is 2-isopropyl-2,3-dihydro-7 -furo[3,2-gr][l]-benzopyran- 3,7- 2 -dione.13... 

Scheme 5 Synthesis of a Depsipeptide from a Hydroxy Derivative Using Isopropenyl Chioroformate/DMAP14-1...

Hydroxyhexanal undergoes a Claisen reaction with isopropenyl acetate in the presence of iV-chlorosuccinimide and tin(ll) chloride as catalyst to afford 2-acetonyloxepane. In the case of 6-hydroxy-2-pentylhexanal, 2-acetonyl-3-pentyloxepane is obtained with 95% diastereoselectivity (Equation 30) <1994CC1123>. 

The transformation could also be performed using a chiral enantiopure enol ether as dienophile. The best results were achieved with the isopropenyl ether 182b derived from cheap and commercially available (—)-(lR,2S,5R)-menthol. The cycloadduct was obtained with an endo/exo-selectivity of 4.1 1 and an induced dia-stereoselectivity of 88 12. Treatment of 178b with trifluoroacetic acid/water 19 1 provided (S)-warfarin 175 in an overall yield of 61% referred to 4-hydroxy coumarin 55 and an enantiomeric excess of 76% (HPLC), which could be increased to 95% ee by recrystallization using the purified endo-product 178b as substrate for the hydrolysis. In the same manner (S)-coumachlor 176 and (S)-acenocoumarol 177 were obtained with 56% overall yield and 93% ee and 59% overall yield and 95% ee, respectively. 

A set of -methylene-/ -hydroxy esters 42 were resolved via enzymatic enantioselective transesterification with Pseudomonas sp. lipase (PCL), free and immobilized one using either vinyl or isopropenyl acetate as acyl donors under different conditions. The corresponding (R)-(+)-acetates (R)-43 and the unreacted (S)-(-)-substrates (S)-42 were obtained with an ee up to >99%.70... 

Sy, L. K. Brown, G. D. Deoxyarteannuin-B, dihydro-deoxyarteannuin-B and tans-5-hydroxy- 2-isopropenyl-5-methylhex-3-en-l-ol from Artemisia anuua. Phytochemistry, 2001, 58(8) 1159-1166. 

Hydroxy-1-oxo- Vl/la, 1, 136f. 8-Hydroxy-1-oxo- IV/lc, 183 a-Tropolon 7-Isopropenyl- V/2c, 730 Zimtaldehyd 4-Methoxy- XIII/2a,... 

E17c, 2533 (Cyclopropan-Spalt.) 6-Hydroxy-4-isopropenyl-l-methyl-XIII/6, 463... 

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