Table 2.

Condition screening for the radiolabeling of (±)-[¹⁸F]7 ((−)-[¹⁸F]7).

Entry	Base	Solvent	Temperature or Microwave	Results
Method 1 for (±)-[18F]7				For (±)-[18F]7
1	K2CO3	MeCN	80 °C	N.P. a
2	K2CO3	DMF	80 °C	N.P.
3	K2CO3	DMSO	90 °C	N.P.
4	K2CO3	1,4-dioxane	90 °C	0.9% b
Method 2 for (±)-[18F]7				For (±)-[18F]20c	For (±)-[18F]7d
5	K2CO3	DMSO	110 °C	4.8% e	N/Af
6	K2CO3	DMSO	110 °C	5.3% g	N/A
7	K2CO3	MeCN	110 °C	16%	4%
Method 3 for (−)-[18F]7
8	TBAHCO3	MeCN	110 °C	11% h	N/A
9	TBAHCO3	MeCN	110 °C	21% i(8%)	N/A
10	TBAHCO3	MeCN	110 °C	29% j(9%)	N/A
11	TBAHCO3	tBuOH/MeCN (3/1, v/v)	110 °C	6.0%	N/A
12	TBAHCO3	DMSO	65 W, 120 s × 2	10%	N/A
13	TBAHCO3	DMF	50 W, 120 s × 2	16% (7%)	N/A
14	Cs2CO3	DMSO	100 °C	1.9%	N/A
15	NaH	DMF	85 °C	47% (37%)	11%
16	NaH	DMF	110 °C	2.1% k	N/A

Note:

^aN.P., no product was detected by HPLC;

^bdecay corrected yield determined by HPLC;

^c[¹⁸F]fluoride incorporation yield determined by radioTLC otherwise noted, the yields in the parenthesis are referred to the decay corrected yield determined by HPLC for the second radiolabeling;

^ddecay corrected yield determined by HPLC;

^ereaction time 10 min;

^fN/A, reaction not performed;

^greaction time 20 min;

^hreaction time 10 min;

ⁱreaction time 20 min;

^jthe precursor was added in three portions;

^kdecay corrected yield determined by HPLC