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. Author manuscript; available in PMC: 2010 Oct 28.
Published in final edited form as: J Am Chem Soc. 2009 Oct 28;131(42):15492–15500. doi: 10.1021/ja9066282

Table 3.

Yields and chirality transfer levels in cyclizations of enantiomeric precursors 15 to give 14agraphic file with name nihms-150630-t0010.jpg

entry precursor R1 R2 R3 R4 R5 er % yield
14b 		er % cte
1 (+)-15a Me Me Me CO2t-Bu H 98.5/1.5 79 91/9 92
2 (−)-15a Me Me Me CO2t-Bu H 85/15 81 84/16 99
3 (+)-15b PMB Me Me CO2t-Bu H 100/0 87 95/5 95
4 (−)-15b PMB Me Me CO2t-Bu H 100/0 85 96/4 96
5 (+)-15c PMB OMe H CO2t-Bu H 99/1 94 93/7 94
6 (−)-15c PMB OMe H CO2t-Bu H 99/1 96 93/7 94
7 (+)-15e PMB TMS Me CO2t-Bu H 100/0 95 95/5 95
8 (−)-15e PMB TMS Me CO2t-Bu H 100/0 93 94/6 96
9 (P)-15f PMB Br Me CO2t-Bu H 99/1 63 95/5 96
10 (M)-15f PMB Br Me CO2t-Bu H 0/100 66 94/6 94
11 (+)-15h PMB Me Me CN H 99.5/0.5 71 93/7 93e
12 (−)-15h PMB Me Me CN H 99/1 68 96/4 97e
13 (+)-15i PMB Me Me Me Me 99/1 57 80/20 81
14 (−)-15i PMB Me Me Me Me 0/100 55 80/20 80
a

Conditions: Bu3SnH and Et3B in 20 mL PhH were added over 2 h via syringe pump to a stirred 10 mM PhH solution of 15.

b

Yield of 14 after isolation by column chromatography on 10% w/w KF/silica gel.

c

Absolute configuration determined by X-ray crystallography.

d

Percent chirality transfer.

e

Neat Bu3SnH and Et3B were added sequentially in one portion to a stirred PhH solution of iodide with [Bu3SnH]i = 5 mM.