Raman tag

1. A method of forming a probe, the method comprising:

converting cholenic acid into a compound with a terminal alkyne group, wherein the converting the cholenic acid comprises using a sequence, wherein the sequence comprises synthesizing a THP-protection group, LiAlH 4 reduction, Dess-Martin oxidation, and Seyferth-Gilbert-Bestmann homologation;

forming alkyne cholesterol (A-Chol) by removing the THP-protection;

forming phenyl-alkyne cholesterol (PhA-Chol) from the compound with the terminal alkyne group via a palladiumcatalyzed Sonogashira reaction; and

forming phenyl-diyne cholesterol (PhDY-Chol) from the compound with the terminal alkyne group via a coppercatalyzed Cadiot-Chodkiewicz reaction.

2. The method of claim 1 , further comprising removing the THP-protection group via an acid.

3. The method of claim 1 , wherein the converting the cholenic acid into the compound with the terminal alkyne group comprises:

adding 3,4-dihydro-2H-pyran (DHP) and p-toluenesulfonic acid monohydrate (p-TsOH) to a mixture of the cholenic acid and THF; and

extracting a first residue, wherein the residue comprises:

4. The method of claim 3 further comprising:

adding the first residue to a suspension of LiAlH 4 in dry THF;

extracting a second residue, wherein the second residue comprises:

5. The method of claim 4 further comprising:

adding Dess-Martin Periodinane to a suspension of the second residue and NaHCO 3 ; and

extracting a third residue, wherein the third residue comprises:

6. The method of claim 5 further comprising:

adding dimethyl-1-diazo-2-oxopropylphosphonate to a solution of the third residue and K 2 CO 3 ;

extracting a fourth residue, wherein the fourth residue comprises:

7. The method of claim 4 further comprising:

adding methanesulfonyl chloride to a solution of the second residue and trimethylamine in CH 2 Cl 2 ;

extracting a fifth residue, wherein the fifth residue comprises:

8. The method of claim 7 further comprising:

adding potassium cyanide to a solution, wherein the solution comprises the fifth residue and DMSO;

extracting a sixth residue, wherein the sixth residue comprises:

9. The method of claim 8 further comprising:

dissolving the sixth residue and p-toluenesulfonic acid monohydrate in THF and methanol;

extracting a seventh residue, wherein the seventh residue comprises:

10. The method of claim 6 further comprising:

dissolving the fourth residue and p-toluenesulfonic acid monohydrate in THF and methanol;

extracting an eighth residue, wherein the eighth residue comprises:

11. The method of claim 6 further comprising:

mixing the fourth residue with CuI, iodobenzene, and trimethylamine;

extracting a ninth residue, wherein the ninth residue comprises:

12. The method of claim 11 further comprising:

dissolving the ninth residue and p-toluenesulfonic acid monohydrate in THF and methanol;

extracting a tenth residue, wherein the tenth residue comprises:

13. The method of claim 6 further comprising:

mixing the fourth residue, CuI, P(o-Tol) 3 , K 2 CO 3 , compound A, and anhydrous EtOH, wherein the compound A comprises:

extracting an eleventh residue, wherein the eleventh residue comprises:

14. The method of claim 13 further comprising:

dissolving the eleventh residue and p-toluenesulfonic acid monohydrate in THF and methanol;

extracting a twelfth residue, wherein the twelfth residue comprises:

15. The method of claim 6 further comprising:

mixing the fourth residue, PdCl 2 (PPh 3 ) 2 , CuI, compound B, and THF, wherein the compound B comprises:

extracting a thirteenth residue, wherein the thirteenth residue comprises:

16. The method of claim 15 further comprising:

dissolving the thirteenth residue and p-toluenesulfonic acid monohydrate in THF and methanol;

extracting a fourteenth residue, wherein the fourteenth residue comprises: