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197721-28-1

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197721-28-1 Usage

Check Digit Verification of cas no

The CAS Registry Mumber 197721-28-1 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,9,7,7,2 and 1 respectively; the second part has 2 digits, 2 and 8 respectively.
Calculate Digit Verification of CAS Registry Number 197721-28:
(8*1)+(7*9)+(6*7)+(5*7)+(4*2)+(3*1)+(2*2)+(1*8)=171
171 % 10 = 1
So 197721-28-1 is a valid CAS Registry Number.

197721-28-1Relevant articles and documents

Wittig Rearrangements of Boron-Based Oxazolidinone Enolates

Zhang, Zirong,Collum, David B.

, p. 10892 - 10900 (2019/09/07)

[2,3]-Sigmatropic rearrangements (Wittig rearrangements) of α-alkoxy oxazolidinone enolates are described. Whereas alkali metal enolates fail, owing to facile deacylation, boron enolates generated from di-n-butylboron triflate and triethylamine rearranged in good yields and high selectivities with exceptions noted. IR and NMR spectroscopies show the boron is chelated by the α-alkoxy group rather than the more distal oxazolidinone carbonyl in the complex and enolate. The rearrangement product contains a boron alkoxide that remains unchelated by either carbonyl. Optimization was guided by density functional theory computations, suggesting that valine-derived oxazolidinones would be superior to the phenylalanine-derived analogues.

An efficient, general asymmetric synthesis of carbocyclic nucleosides: Application of an asymmetric aldol/ring-closing metathesis strategy

Crimmins,King,Zuercher,Choy

, p. 8499 - 8509 (2007/10/03)

A general and efficient synthesis of carbocyclic and hexenopyranosyl nucleosides has been developed. The strategy combines three key transformations: an asymmetric aldol addition to establish the relative and absolute configuration of the pseudosugar, a ring-closing metathesis to construct the pseudosugar ring, and a Trost-type palladium(0)-mediated substitution to assemble the pseudosugar and the aromatic base. Carbovir, abacavir, and their 2'-methyl derivatives as well as hexenopyranosyl nucleoside analogues have been prepared by this sequence.

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