Table 1. Condition Optimization of the Condensation Reaction (I) and the Phosphorylation Reaction (II)^a.

	I		II			III
entry	solvent	pyridine (equiv.)	deprotonating agent	T (°C)	T (h)	LCAP of 1 (%)d	d.r. ratioe (1/13)
1	pyridineb		MeMgCl	–10	2	96.7	161/1
2	THFc		MeMgCl	–10	2	93.0	36/1
3	THFc	1.0	MeMgCl	–10	2	92.7	42/1
4	pyridineb		MeMgCl	–20	2	92.9	232/1
5	pyridineb		t-BuMgCl	–20	2	94.1	783/1

^aGeneral procedure: the condensation reaction of compound 5 (500 mg, 1.72 mmol, 1 equiv.) and DMF-DMA (820 mg, 6.88 mmol, 4.0 equiv.) afforded compound 9. The coupling of the obtained crude 9 and compound 10 (1.02 g, 2.06 mmol, 1.2 equiv.) was performed in the presence of the deprotonating agent (2.58 mmol, 1.5 equiv.). When crude 9 disappeared, the phosphorylation was quenched with aq. NH₄Cl solution and provided compound 12. After simple aftertreatment, crude 12 was subjected to the solution of acetic acid (2.06 g, 34.4 mmol, 20.0 equiv.). Finally, product 1 was obtained.

^bThe condensation was conducted at 25 °C for 3 h.

^cThe condensation was conducted at 60 °C for 3 h.

^dLCAP: the area (%) of compound 1 determined by HPLC in the final reaction mixture.

^eThe d.r. ratio was determined by HPLC.