secondary hydroxy group
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2022 ◽  
Vol 18 ◽  
pp. 95-101
Author(s):  
Sandeep Kumar ◽  
Jyotirmoy Maity ◽  
Banty Kumar ◽  
Sumit Kumar ◽  
Ashok K Prasad

Conformationally restricted diastereomeric homoarabinofuranosylpyrimidines (AZT analogue), i.e., (5′R)-3′-azido-3′-deoxy-2′-O,5′-C-bridged-β-ᴅ-homoarabinofuranosylthymine and -uracil had been synthesized starting from diacetone ᴅ-glucofuranose following chemoenzymatic and chemical routes in 34–35% and 24–25% overall yields, respectively. The quantitative and diastereoselective acetylation of primary hydroxy over two secondary hydroxy groups present in the key nucleoside precursor was mediated with Lipozyme® TL IM in 2-methyltetrahydrofuran following a chemoenzymatic pathway. Whereas, the protection of the primary hydroxy over the lone secondary hydroxy group in the key azido sugar precursor was achieved using bulky tert-butyldiphenylsilyl chloride (TBDPS-Cl) in pyridine in 92% yield following a chemical synthetic pathway. The chemoenzymatic method was found to be superior over the chemical method in respect of the number of synthetic steps and overall yield of the final product.


2018 ◽  
Vol 14 ◽  
pp. 1229-1237
Author(s):  
Anna Czarnecka ◽  
Emilia Kowalska ◽  
Agnieszka Bodzioch ◽  
Joanna Skalik ◽  
Marek Koprowski ◽  
...  

We present a successful deoxygenation reaction of ortho-1,3-dithianylaryl(aryl)methanols which enables a selective removal of the secondary hydroxy group in presence of the 1,3-dithianyl moiety under reductive conditions. This reaction proceeds well with ZnI2/Na(CN)BH3 in dichloroethane or benzene for both unsubstituted and substituted aryls (by electron-rich groups). This is leading to formyl-protected diarylmethanes with potential application in the synthesis of new pharmaceuticals and optoelectronic materials. This synthetic approach gives an access to a wide variety of functionalized ortho-1,3-dithianylaryl(aryl)methanes in 26–95% yields and is recommended for the substrates containing sulfur atoms, for which transition metal-induced reactions fail.


2016 ◽  
Vol 11 (9) ◽  
pp. 1934578X1601100 ◽  
Author(s):  
Stefano Serra ◽  
Davide De Simeis

We here describe a study of the enzyme-mediated acylation reaction of 6,7-dihydroxy-linalool stereoisomers, which are natural triols occurring in different vegetal species. We found that only few lipases are able to catalyze the acylation of the secondary hydroxy group present in these isomers and only lipase from Candida rugosa and novozyme 435 provide either (3 R,6 R)-6-acetoxy-7-hydroxylinalool or (3 R,6 S)-6-acetoxy-7-hydroxylinalool in moderate and very good isomeric purity, respectively Even for these favorable cases the reaction proceeds very sluggishly. Our finding can give a sensible interpretation to the fact that 6-acyl-7-hydroxy-linalool derivatives do not occur in nature, whereas the corresponding glycosides, whose formation is catalyzed by glycosidase, are very common.


2006 ◽  
Vol 71 (8) ◽  
pp. 1131-1160 ◽  
Author(s):  
Martin Dračínský ◽  
Simona Hybelbauerová ◽  
Jan Sejbal ◽  
Miloš Buděšínský

New lupane-type triterpenoids with 5(6) double bond were prepared using the method of partial demethylation on carbon C-4. Hydroboration of the double bond led to 6α-hydroxy derivative. By the oxidation and following reduction of 6α-hydroxy derivative the 6-oxo and 6β-hydroxy derivatives were prepared. A new method for selective oxidation of secondary hydroxy group in the presence of primary hydroxy group was performed. The conformation of ring A of new lupane-type 3-oxo derivatives with a substituent on ring B was elucidated on the bases of 1H and 13C NMR spectra and molecular modelling.


1999 ◽  
Vol 10 (13) ◽  
pp. 2497-2500 ◽  
Author(s):  
Patrizia Ferraboschi ◽  
Fabio Pecora ◽  
Shahrzad Reza-Elahi ◽  
Enzo Santaniello

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